ProboStat webinar: Fixed bed reactor
Introduces the Fixed Bed Reactor accessory for ProboStat. Exchangeable glass or quartz frit tubes for plain catalytic activity testing, thermocouple inside the catalyst bed, plus the possibility to add electrodes to study effects of electrical fields, currents, or plasma.
These articles refer to ProboStat or other NORECS products, filtered with keywords: 'catalytic, catalyst, fixed bed reactor'
ID=716
MOX-Based Resistive Gas Sensors with Different Types of Sensitive Materials (Powders, Pellets, Films), Used in Environmental Chemistry
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Chemosensors
Volume: 11,
Issue: 2,
Pages: 95 Time of Publication: 2023 |
| Abstract | The identification of an unknown gaseous species or the composition of a gaseous mixture can be performed using various experimental techniques such as: mass spectrometry, chromatography, nuclear magnetic resonance (NMR), infrared (IR), X-Rays, or by combining these analytical techniques (in automated analyzers). Unfortunately, these techniques use highly expensive equipment and require the use of qualified personnel. Using gas sensors is a viable and inexpensive alternative. The most commonly used sensors in the field are resistive type chemosensors (chemiresistors), due to their simple detection mechanism and low manufacturing costs. The detection principle of these sensors is based on the catalytic reaction between the sensitive material of the sensor and the target gas. This reaction occurs with the release or consumption of electrons, influencing the overall electrical resistance of the sensor. This review describes various MOX-based chemiresistors, which contain different types of sensitive substrates, such as powders, pellets or films, as well as a clear tendency towards sensor miniaturization and the constant improvement of the fabrication techniques towards greener and more cost-effective synthesis routes over time. The goal of this research was to obtain sensors with high 3S parameters (sensitivity, selectivity, and stability), that can be mass-produced and implemented on a wide scale. |
| Keywords | resistive gas sensors; chemiresistors; sensitivity; selectivity; stability; eco-friendly; low-cost; miniaturized; micro-sensors; mass-produced |
| Remark |
https://doi.org/10.3390/chemosensors11020095 Link |
ID=713
Effect of Steam to Carbon Dioxide Ratio on the Performance of a Solid Oxide Cell for H2O/CO2 Co-Electrolysis
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Nanomaterials
Volume: 13,
Issue: 2,
Pages: 299 Time of Publication: 2023 |
| Abstract | The mixture of H2 and CO, the so-called syngas, is the value-added product of H2O and CO2 co-electrolysis and the feedstock for the production of value-added chemicals (mainly through Fischer-Tropsch). The H2/CO ratio determines the process in which syngas will be utilized and the type of chemicals it will produce. In the present work, we investigate the effect of H2O/CO2 (steam/carbon dioxide, S/C) ratio of 0.5, 1 and 2 in the feed, on the electrochemical performance of an 8YSZ electrolyte-supported solid oxide cell and the H2/CO ratio in the outlet, under co-electrolysis at 900 °C. The B-site iron doped lanthanum strontium chromite La0.75Sr0.25Cr0.9Fe0.1O3-δ (LSCF) is used as fuel electrode material while as oxygen electrode the state-of-the art LSM perovskite is employed. LSCF is a mixed ionic-electronic conductor (MIEC) operating both under a reducing and oxidizing atmosphere. The cell is electrochemically characterized under co-electrolysis conditions both in the presence and absence of hydrogen in the feed of the steam and carbon dioxide mixtures. The results indicate that under the same concentration of hydrogen and different S/C ratios, the same electrochemical performance with a maximum current density of approximately 400 mA cm−2 is observed. However, increasing p(H2) in the feed results in higher OCV, smaller iV slope and Rp values. Furthermore, the maximum current density obtained from the cell does not seem to be affected by whether H2 is present or absent from the fuel electrode feed but has a significant effect on the H2/CO ratio in the analyzed outlet stream. Moreover, the H2/CO ratio seems to be identical under polarization at different current density values. Remarkably, the performance of the LSCF perovskite fuel electrode is not compromised by the exposure to oxidizing conditions, showcasing that this class of electrocatalysts retains their reactivity in oxidizing, reducing, and humid environments. |
| Keywords | Co-electrolysis; perovskite oxide; doping; lanthanum chromite; LSCF; solid oxide; SOEC; syngas; steam to carbon dioxide ratio |
| Remark |
https://doi.org/10.3390/nano13020299 Link |
ID=710
Low temperature ammonia synthesis by surface protonics over metal supported catalysts
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Faraday Discussions
Time of Publication: 2023
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| Abstract | Low-temperature ammonia synthesis by applying an electric field to a solid heterogeneous catalyst was investigated to realize an on-demand, on-site catalytic process for converting distributed renewable energy into ammonia. By applying an electric field to the catalyst, even at low temperatures, the reaction proceeds efficiently by an "associative mechanism" in which proton-conducting species on the support surface promote the formation of N2Had intermediates through surface protonics. Kinetics, isotope exchange, infrared spectroscopy, X-ray spectroscopy, and AC impedance analysis were performed to clarify the effect of metal and catalyst support structure on the reaction, and an evaluation method for the surface protonics of the support was established to analyze the reaction mechanism, and further analysis using computational chemistry was also conducted. The elementary step determining catalytic activity changed from N2 dissociation to N2H formation, and this difference resulted in high activity for ammonia synthesis at low temperatures even when using base metal catalysts such as Fe and Ni. |
| Remark |
DOI: 10.1039/x0xx00000x Link |
ID=707
Surface protonic conductivity in chemisorbed water in porous nanoscopic CeO2
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Applied Surface Science
Volume: 611,
Issue: A,
Pages: 155590 Time of Publication: 2023 |
| Abstract | CeO2 surfaces play decisive roles in heterogeneous catalysis of important processes. Here, we investigate adsorption and dissociation of water and migration of protons on internal surfaces of nanoscopic porous CeO2. Sorption and thermogravimetry confirm literature suggestions that the surface is hydrogenated to Ce3+ ions and protons H+. The following chemisorption is dissociative, yet weak, and physisorption sets in only at the very highest relative humidities, reflecting hydrophobic behaviour. We link sample conductivities to surface protonic conductances via a brick layer model and show that behaviours at high, intermediate, and low temperatures with, respectively, positive, close to zero, and negative apparent activation energies and pH2O1/2, pH2O1, and pH2O3/2 dependences, can be attributed to different models of migration all within the chemisorbed layer, without contribution from physisorbed water. While CeO2 may special in this respect due to the effect of the hydrogenated surface, we believe the extended models of transport in the chemisorbed layer may apply also to other oxides. Unsaturated chemisorption may play an important role for CeO2 as catalyst in that the surface is left available for reactant molecules, still with availability of dissociated and mobile protons in the chemisorbed layer and electronic defects by Ce3+ in the surface. |
| Keywords | Ceria; CeO2; Porous; Hydrogenation; Water adsorption; Chemisorption; Conductivity; Protonic; Surface; Brick layer model |
| Remark |
https://doi.org/10.1016/j.apsusc.2022.155590 Link |
ID=706
Ni-doped A-site excess SrTiO3 thin films modified with Au nanoparticles by a thermodynamically-driven restructuring for plasmonic activity
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Catalysis Today
Time of Publication: 2023
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| Abstract | Plasmonically active nanoparticles offer a promising pathway to extend the absorption range of photocatalysts. While not necessarily catalytically active themselves, these particles allow the absorption of lower energy photons in wide band gap photocatalysts. Here, we present A-site excess SrTiO3 thin films, doped with Ni, where through a subsequent exsolution process we created well-socketed Ni nanoparticles in the surface of SrTiO3. These were galvanically replaced by Au, resulting in well-socketed Au nanoparticles with variable size on the surface, depending on the galvanic replacement time. Photoelectrochemical measurements and electron energy loss spectroscopy revealed the improved photoresponse of the thin films by plasmonic activity of the nanoparticles. The energy of the plasmon peak suggests that the main improvement results from the injection of hot charge carriers. Our study opens new avenues for the design and synthesis of the next generation of photocatalytic materials. |
| Remark |
In press, https://doi.org/10.1016/j.cattod.2022.11.011 Link |
ID=698
Effects of Ni-NCAL and Ni–Ag electrodes on the cell performances of low-temperature solid oxide fuel cells with Sm0.2Ce0·8O2-δ electrolyte at various temperatures
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International Journal of Hydrogen Energy
Volume: 47,
Issue: 94,
Pages: 40067-40082 Time of Publication: 2022 |
| Abstract | Three low-temperature solid oxide fuel cells are built using Sm0.2Ce0·8O2-δ (SDC) as the electrolyte. Cell A is symmetrical and features Ni–LiNi0.8Co0·15Al0·05O2 (Ni–NCAL) electrodes, Cell B comprises a Ni–NCAL anode and a Ni–Ag cathode, and Cell C is fabricated using a Ni–NCAL cathode and a Ni–Ag anode. The ohmic resistance and polarization resistance (Rp) of Cells B and C are significantly higher than those of Cell A. The reduction of NCAL at the anodes of Cells A and B yields LiOH and Li2CO3 phases, and the Ni particles generated on the surfaces of the NCAL particles improve the catalytic activity of the cells. Li2CO3–LiOH melts at temperatures >450 °C and penetrates the porous SDC electrolyte layer, causing its densification and abnormal grain growth and increasing its ionic conductivity to >0.2 S/cm at low temperatures. The high open-circuit voltages (OCVs) (0.970–1.113 V) of the cells during electrochemical measurements are ascribed to the Li2CO3–LiOH phase which serves as an electron-blocking layer for the SDC electrolytes. As the reduction of NCAL approaches completion, the anode comprises only Ni phase, which hinders the charge transfer process. The triple-phase-boundary (TPB) area at cathode of Cell B is significantly lower than that of Cell A; therefore, the catalytic activity of Cell B for the oxygen reduction reaction is lower than that of Cell A. Consequently, the maximum power density (MPD) of Cell B is less than half of that of Cell A. The large Rp value of Cell C is ascribed to its low TPB area at Ni–Ag anode which has no reaction with H2 during operation. No visible sintering of the SDC electrolyte layer is observed for Cell C; therefore, its ionic conductivity is considerably smaller than those of the electrolyte layers of Cells A and B. The OCVs of Cell C (0.281–0.495 V) are significantly lower than the typical OCVs of ceria-based SOFCs. This is attributed to the porous SDC electrolyte layer of Cell C. The large Rp values and the low OCVs contribute to the low MPDs of Cell C at various temperatures. |
| Keywords | Solid oxide fuel cell; NCAL electrode; Polarization; Cell performance |
| Remark |
https://doi.org/10.1016/j.ijhydene.2022.09.148 Link |
ID=691
Effects of LiNi0.8Co0.15Al0.05O2 electrodes on the conduction mechanism of Sm0.2Ce0.8O2−δ electrolyte and performance of low-temperature solid oxide fuel cells
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Journal of Power Sources
Volume: 546,
Pages: 231995 Time of Publication: 2022 |
| Abstract | In this study, three low-temperature solid oxide fuel cells are constructed using Ce0.8Sm0.2O2−δ (SDC) as the electrolyte and Ni–LiNi0.8Co0.15Al0.05O2 (Ni–NCAL) and Ni–Ag as the electrodes. Cell A with symmetrical Ni–NCAL electrodes exhibits the best electrochemical performance. During operation, the Ni–NCAL anode is reduced by H2 atmosphere to form LiOH and Li2CO3. The Li2CO3–LiOH melt produced at >450 °C permeates the SDC electrolyte layer, causing its densification and grain growth in addition to the Li+-ion doping of SDC grains. The maximum electrical conductivity of the Li+-ion-doped SDC at 550 °C is at least one order of magnitude smaller than that of the SDC–Li2CO3–LiOH composite electrolyte (0.331 S cm−1). The ohmic and polarization resistances of Cell A at 550 °C are 0.168 and 0.256 Ω cm2, respectively, and its open-circuit voltage is 1.065 V, indicating the presence of dense SDC electrolyte and electron-blocking layers. The maximum power density of the cell at 550 °C is 535.2 mW·cm−2, which is primarily due to the high catalytic activity for the hydrogen oxidation and oxygen reduction reactions at the electrodes and large electrical conductivity of the SDC–Li2CO3–LiOH composite electrolyte at low temperatures. |
| Remark |
https://doi.org/10.1016/j.jpowsour.2022.231995 Link |
ID=662
Unlocking bulk and surface oxygen transport properties of mixed oxide-ion and electron conducting membranes with combined oxygen permeation cell and oxygen probe method
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Journal of Membrane Science Volume: 644, Pages: 120082 Time of Publication: 2022 |
| Abstract | Surface exchange kinetics and bulk diffusion of oxygen are of paramount importance to the activity of oxygen electrocatalysis and performance of electrochemical devices such as fuel cell, metal-air batteries, and oxygen separation membranes. Conventional approaches to obtaining these transport properties are often limited to single property under a specific non-operation related condition. Here we use a combined oxygen permeation cell and oxygen probe methodology to simultaneously attain rates of oxygen surface exchange and bulk conductivity/chemical diffusivity of three representative mixed oxide-ion and electron conductors, namely SrCo0.9Ta0.1O3-δ (SCT), La0.6Sr0.4CoO3-δ (LSC) and La0.6Sr0.4FeO3-δ (LSF), operated under a steady-state oxygen flux. The results explicitly show that SCT exhibit the highest oxide-ion conductivity/chemical diffusivity, fastest rates of surface oxygen exchange kinetics, thus promising to be the best oxygen electrocatalyst. We have also mapped out the distribution of oxygen chemical potential gradient across the membranes and applied B-transport number concept to illustrate the rate-limiting steps in the overall oxygen permeation process. |
| Remark | Link |
ID=636
Enhanced activity of catalysts on substrates with surface protonic current in an electrical field – a review
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Chem. Commun.
Volume: 57,
Pages: 5737 Time of Publication: 2021 |
| Abstract | It has over the last few years been reported that the application of a DC electric field and resulting current over a bed of certain catalyst-support systems enhances catalytic activity for several reactions involving hydrogen-containing reactants, and the effect has been attributed to surface protonic conductivity on the porous ceramic support (typically ZrO2, CeO2, SrZrO3). Models for the nature of the interaction between the protonic current, the catalyst particle (typically Ru, Ni, Co, Fe), and adsorbed reactants such as NH3 and CH4 have developed as experimental evidence has emerged. Here, we summarize the electrical enhancement and how it enhances yield and lowers reaction temperatures of industrially important chemical processes. We also review the nature of the relevant catalysts, support materials, as well as essentials and recent progress in surface protonics. It is easily suspected that the effect is merely an increase in local vs. nominal set temperature due to the ohmic heating of the electrical field and current. We address this and add data from recent studies of ours that indicate that the heating effect is minor, and that the novel catalytic effect of a surface protonic current must have additional causes. |
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ID=624
Metal-Support Interaction and Electrochemical Promotion of Nano- Structured Catalysts for the Reverse Water Gas Shift Reaction
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Time of Publication: 2021
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| Abstract | ii Abstract The continued release of fossil-fuel derived carbon dioxide (CO2) emissions into our atmosphere led humanity into a climate and ecological crisis. Converting CO2 into valuable chemicals and fuels will replace and diminish the need for fossil fuel-derived products. Through the use of a catalyst, CO2 can be transformed into a commodity chemical by the reverse water gas shift (RWGS) reaction, where CO2 reacts with renewable hydrogen (H2) to form carbon monoxide (CO). CO then acts as the source molecule in the Fischer-Tropsch (FT) synthesis to form a range of hydrocarbons to manufacture chemicals and fuels. While the FT synthesis is a mature process, the conversion of CO2 into CO has yet to be made commercially available due to the constraints associated with high reaction temperature and catalytic stability. Noble metal ruthenium (Ru) has been widely used for the RWGS reaction due to its high catalytic activity, however, several constraints hinder its practical use, associated with its high cost and its susceptibility to deactivation. The doping or bimetallic use of non-noble metals iron (Fe) and cobalt (Co) is an attractive option to lower material cost and tailor the selectivity of the CO2 conversion towards the RWGS reaction without compromising catalytic activity. Furthermore, employing nanostructured catalysts as nanoparticles is a viable solution to further lower the amount of metal used and utilize the highly active surface area of the catalyst. Dispersing nanoparticles on ionically conductive supports/solid electrolytes which contain species like O2-, H+, Na+, and K+, provide an approach to further enhance the reaction. This phenomenon is referred to as metal-support interaction (MSI), allowing for the ions to back spillover from the support and onto the catalyst surface. An in-situ approach referred to as Non-Faradaic Modification of catalytic activity (NEMCA), also known as electrochemical promotion of catalysis (EPOC) is used to in- situ control the movement of ionic species from the solid electrolyte to and away from the catalyst. Both the MSI and EPOC phenomena have been shown to be functionally equivalent, meaning the ionic species act to alter the work function of the catalyst by forming an effective neutral double layer on the surface, which in turn alters the binding energy of the reactant and intermediate species to promote the reaction. The main objective of this work is to develop a catalyst that is highly active and selective to the RWGS reaction at low temperatures (< 400 °C) by employing the MSI and EPOC iii phenomena to enhance the catalytic conversion. The electrochemical enhancement effect will lower energy requirements and allow the RWGS reaction to take place at moderate temperatures. Catalysts composed of Ru, Fe and Co were synthesized through the polyol synthesis technique and deposited on mixed-ionically conductive and ionically conductive supports to evaluate their performance towards the RWGS reaction and the MSI effect. The nano-structured catalysts are deposited as free-standing nanoparticles on solid electrolytes to in-situ promote the catalytic rate through the EPOC phenomenon. Furthermore, Density Functional Theory (DFT) calculations were performed to correlate theory with experiment and elucidate the role polarization has on the binding energy of reactant and intermediate species. The high dispersion of RuFe nanoparticles on ion-containing supports like samarium- doped ceria (SDC) and yttria-stabilized zirconia (YSZ) led to an increase in the RWGS activity due to the MSI effect. A direct correlation between experimental and DFT modeling was established signifying that polarization affected the binding energy of the CO molecule on the surface of Ru regardless of the type of ionic species in the solid electrolyte. The electrochemical enhancement towards the RWGS reaction has been achieved with iron-oxide (FeOx) nanowires on YSZ. The in-situ application of O2- ions from YSZ maintained the most active state of Fe3O4 and FeO towards the RWGS reaction and allowed for persistent-promoted state that lasted long after potential application. Finally, the deposition of FeOx nanowires on Co3O4 resulted in the highest CO2 conversion towards the RWGS reaction due to the metal-oxide interaction between both metals, signifying a self-sustained electro-promoted state. |
| Remark |
Thesis submitted to the University of Ottawa in partial Fulfillment of the requirements for the Degree of Doctor of Philosophy Link |
ID=604
Tuning the RWGS Reaction via EPOC and In Situ Electro-oxidation of Cobalt Nanoparticles
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ACS Catal.
Volume: 10,
Issue: 24,
Pages: 14916–14927 Time of Publication: 2020 |
| Abstract | The electrochemical promotion of catalytic activity by non-noble transition metals is rarely reported in the literature. Here, Co nanoparticles were utilized for the electrochemical activation of CO2 hydrogenation under atmospheric pressure conditions. A range of transient kinetic experiments in conjunction with X-ray photoelectron spectroscopy and imaging techniques were employed to correlate the observed catalytic activity with the electronic and morphological characteristics of the cobalt catalyst surface. Our results show that migrating ions from the solid electrolyte to the catalyst surface has a dual effect, which has an impact on the observed catalytic behavior. First, they lead to an electrochemically formed double layer on the catalyst surface, which effectively modifies the catalyst work function and consequently alters the observed catalytic rate. Second, they have a profound effect on the oxidation state of cobalt and therefore on the structure of the cobalt oxide particles formed. The presence of Co oxide phases upon anodic polarization shows up to a 5-fold increase in the catalytic rate of the reverse water gas shift (RWGS) reaction. The enhancement of the catalytic activity observed in this work, with a relatively inexpensive cobalt oxide film, is comparable to that obtained with noble metal catalysts in classical EPOC studies. The present study also demonstrates that the formation of different oxide phases can be controlled accurately by electrochemical means and used to tune the catalytic activity and selectivity of cobalt. The reported results could guide the design and operation of more selective and active catalytic processes for the RWGS reaction. |
| Keywords | electrochemical promotion, cobalt oxide, CO2 hydrogenation, XPS, RWGS |
| Remark | Link |
ID=578
In-situ Ni exsolution from NiTiO3 as potential anode for solid oxide fuel cells
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International Journal of Hydrogen Energy Volume: 45, Issue: 43 Time of Publication: 2020 |
| Abstract | Sample NiTiO3 (NTO) is prepared by the molten salts synthesis route as a potential anode material for solid oxide fuel cell (SOFC) applications. An additional sample impregnated with 5 mol%Ni (N-NTO) is also presented. Structural characterization reveal a pure NiTiO3 phase upon calcination at 850 °C and 1000 °C. Redox characterization by temperature programmed reduction tests indicate the transition from NiTiO3 to Ni/TiO2 at ca. 700 °C. Ni nanoparticles (ca. 26 nm) are exsolved in-situ from the structure after a reducing treatment at 850 °C. Catalytic activity tests for partial oxidation of methane performed in a fixed bed reactor reveal excellent values of activity and selectivity due to the highly dispersed Ni nanoparticles in the support surface. Time-on-stream behavior during 100 h operation in reaction conditions for sample N-NTO yield a stable CH4 conversion. Electrolyte supported symmetrical cells are prepared with both materials achieving excellent polarization resistance of 0.023 Ω cm2 in 7%H2/N2 atmosphere at 750 °C with sample N-NTO. The maximum power density achieved is of 273 mW cm−2 at 800 °C with a commercial Pt ink used as a reference cathode, indicating further improvement of the system can be achieved and positioning the N-NTO material as a promising SOFC anode material. |
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ID=577
Support effects on catalysis of low temperature methane steam reforming
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RSC Adv.
Volume: 10,
Pages: 26418-26424 Time of Publication: 2020 |
| Abstract | Low temperature (<500 K) methane steam reforming in an electric field was investigated over various catalysts. To elucidate the factors governing catalytic activity, activity tests and various characterization methods were conducted over various oxides including CeO2, Nb2O5, and Ta2O5 as supports. Activities of Pd catalysts loaded on these oxides showed the order of CeO2 > Nb2O5 > Ta2O5. Surface proton conductivity has a key role for the activation of methane in an electric field. Proton hopping ability on the oxide surface was estimated using electrochemical impedance measurements. Proton transport ability on the oxide surface at 473 K was in the order of CeO2 > Nb2O5 > Ta2O5. The OH group amounts on the oxide surface were evaluated by measuring pyridine adsorption with and without H2O pretreatment. Results indicate that the surface OH group concentrations on the oxide surface were in the order of CeO2 > Nb2O5 > Ta2O5. These results demonstrate that the surface concentrations of OH groups are related to the proton hopping ability on the oxide surface. The concentrations reflect the catalytic activity of low-temperature methane steam reforming in the electric field. |
| Remark | Link |
ID=571
Electrochemical promotion of Ru nanoparticles deposited on a proton conductor electrolyte during CO2 hydrogenation
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Applied Catalysis B: Environmental
Volume: 276,
Pages: 119148 Time of Publication: 2020 |
| Abstract | Recycling CO2 into a carbon-neutral source is a beneficial approach in reducing non-renewable energy sources. Herein, the electrochemical promotion of catalysis (EPOC) has been exploited to enhance the catalytic activity of Ru nanoparticles (0.7−1�¯nm) deposited on the proton conductor yttria-doped barium zirconate (BZY), as free-standing nanoparticles and supported on Co3O4 semiconductor, for CO2 hydrogenation. Under 250−450�¯°C and atmospheric pressure, both methanation and reverse water-gas shift (RWGS) reaction take place simultaneously over the Ru nanoparticles with a superior selectivity to CO. Under anodic polarization, free-standing Ru nanoparticles displayed an increase in CH4 and a decrease in CO production, while the opposite effect was observed under cathodic polarization. Ru supported on Co3O4 displayed a superior catalytic activity mostly due to enhanced metal–support interactions. The electronic effects induced by the pairing of Co3O4 and BZY resulted in a new approach to EPOC applications that brings it closer to industrial application. |
| Remark | Link |
ID=565
Artificial photosynthesisAdvanced nanomaterials and use of biocatalystsfor novel photoelectrochemical cells
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Time of Publication: 2020
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| Remark |
Thesis submitted for the degree of Philosophiae Doctor, University of Oslo Link |
ID=560
Reaction mechanism of low-temperature catalysis by surface protonics in an electric field
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Faraday Discuss.
Time of Publication: 2020
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| Abstract | The process combining heterogeneous catalysts and DC electric field can achieve high catalytic activities, even under mild conditions (<500 K) with less electrical energy consumption. Hydrogen production by steam reforming of methane, aromatics and alcohol, dehydrogenation of methylcyclohexane, dry reforming of methane, and ammonia synthesis are known to proceed at low temperatures in an electric field. In-situ/operando analyses have been conducted using IR, Raman, XAFS, electrochemical impedance spectroscopy, and isotopic kinetic analyses to elucidate the reaction mechanism for these reactions at low temperatures. Results show that surface proton hopping by a DC electric field, called surface protonics, is important for these reactions at low temperatures because of higher surface adsorbate concentrations at lower temperatures. |
| Remark |
Accepted Manuscript, https://doi.org/10.1039/C9FD00129H Link |
ID=557
Activation of C−H Bond of Propane by Strong Basic Sites Generated by Bulk Proton Conduction on V‐Modified Hydroxyapatites for the Formation of Propene
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ChemCatChem
Volume: 12,
Issue: 9,
Pages: 2506-2521 Time of Publication: 2020 |
| Abstract | Insights into the catalytic transformation of propane to propene on V‐apatite catalysts are provided based on structure‐reactivity relationships. Substitution of phosphates by vanadates in the hydroxyapatite structure leads to the formation of Ca10(PO4)6‐x(VO4)x(OH)2‐yOy V‐oxy‐hydroxy‐apatite solid solutions (x=0→6). Bulk vanadium incorporation promotes (i) calcium rich terminations (XPS, CO adsorption), (ii) proton deficiency inside the OH− channels (1H NMR) giving rise to O2− native species, (iii) the thermally‐activated formation of additional O2− species along the OH− channels resulting in H‐bonding interaction (in situ DRIFT) and (iv) the proton conduction process that eventually results in the surface exposure of O2− species (in situ impedance spectroscopy). The exposure of Ca2+−O2− surface acid‐base pairs allows the dissociation of hydrogen, emphasizing the strong basicity of the related O2− species. Whereas an increasing vanadium content is beneficial to propene selectivity, it scarcely impacts propane conversion. The reaction proceeds mainly upon oxidative dehydrogenation, even if the minor dehydrogenation route is also observed. Surface O2− generated thanks to proton mobility are involved in the C−H bond activation, as shown by the synergistic effect between the oxidative dehydrogenation of propane reaction and the bulk proton conduction measured under operando conditions. This puts emphasis on the key role of strong basic sites for propane activation. |
| Remark |
https://doi.org/10.1002/cctc.201902181 Link |
ID=556
First observation of surface protonics on SrZrO3 perovskite under a H2 atmosphere
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Chem. Commun.
Volume: 56,
Pages: 2699-2702 Time of Publication: 2020 |
| Abstract | This is the first direct observation that surface proton hopping occurs on SrZrO3 perovskite even under a H2 (i.e. dry) atmosphere. Understanding proton conduction mechanisms on ceramic surfaces under a H2 atmosphere is necessary to investigate the role of proton hopping on the surface of heterogeneous catalysts in an electric field. In this work, surface protonics was investigated using electrochemical impedance spectroscopy (EIS). To extract the surface proton conduction, two pellets of different relative densities were prepared: a porous sample (R.D. = 60%) and a dense sample (R.D. = 90%). Comparison of conductivities with and without H2 revealed that only the porous sample showed a decrease in the apparent activation energy of conductivity by supplying H2. H/D isotope exchange tests revealed that the surface proton is the dominant conductive species over the porous sample with H2 supply. Such identification of a dominant conductive carrier facilitates consideration of the role of surface protonics in chemical reactions. |
| Remark | Link |
ID=552
High performance and toxicity assessment of Ta3N5 nanotubes for photoelectrochemical water splitting
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Catalysis Today
Time of Publication: 2019
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| Abstract | In this work, Co-based cocatalysts are electrodeposited on mesoporous Ta3N5 nanotubes. The electrodeposition time is varied and the optimized photoelectrode reaches a photocurrent density of 6.3 mA/cm2 at 1.23 V vs. SHE, under simulated solar illumination of 1 Sun, in 1 M NaOH. The best performing electrode, apart from the high photocurrent density, shows improved stability under intense photoelectrochemical water splitting conditions. The dual function of the cocatalyst to improve not only the photoelectrochemical performance, but also the stability, is highlighted. Moreover, we adopted a simple protocol to assess the toxicity of Co and Ta contained nanostructured materials (representing used photoelectrodes) employing the human cell line HeLa S3 as target cells. |
| Remark |
https://doi.org/10.1016/j.cattod.2019.12.031 Link |
ID=551
A CO2-Tolerant Perovskite Oxide with High Oxide Ion and Electronic Conductivity
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Adv. Mater.
Time of Publication: 2019
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| Abstract | Mixed ionic–electronic conductors (MIECs) that display high oxide ion con-ductivity (σo) and electronic conductivity (σe) constitute an important family of electrocatalysts for a variety of applications including fuel cells and oxygen sepa-ration membranes. Often MIECs exhibit sufficient σe but inadequate σo. It has been a long-standing challenge to develop MIECs with both high σo and stability under device operation conditions. For example, the well-known perovskite oxide Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) exhibits exceptional σo and electrocatalytic activity. The reactivity of BSCF with CO2, however, limits its use in practical applications. Here, the perovskite oxide Bi0.15Sr0.85Co0.8Fe0.2O3−δ (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σo among the highest for known MIECs, but also high CO2 tolerance. When used as an oxygen separation membrane, BiSCF displays high oxygen permeability comparable to that of BSCF and much higher stability under CO2. The combination of high oxide transport properties and CO2 tolerance in a single-phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications. |
| Remark |
DOI: 10.1002/adma.201905200 Link |
ID=544
Mn-rich SmBaCo0.5Mn1.5O5+δ double perovskite cathode material for SOFCs
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International Journal of Hydrogen Energy
Volume: 44,
Issue: 50
Time of Publication: 2019
|
| Abstract | SmBaCo0.5Mn1.5O5+δ oxide with Sm-Ba cation-ordered perovskite-type structure is synthesized and examined in relation to whole RBaCo0.5Mn1.5O5+δ series (R: selected rare earth elements). Presence of Sm and 3:1 ratio of Mn to Co allows to balance physicochemical properties of the composition, with moderate thermal expansion coefficient value of 18.70(1)·10−6 K−1 in 300–900 °C range, high concentration of disordered oxygen vacancies in 600–900 °C range (δ = 0.16 at 900 °C), and good transport properties with electrical conductivity reaching 33 S cm−1 at 900 °C in air. Consequently, the compound enables to manufacture catalytically-active cathode, with good electrochemical performance measured for the electrolyte-supported laboratory-scale solid oxide fuel cell with Ni-Gd1.9Ce0.1O2-δ|La0.4Ce0.6O2-δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ configuration, for which 1060 mW cm−2 power density is observed at 900 °C. Furthermore, the tested symmetrical SmBaCo0.5Mn1.5O5+δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ cell delivers 377 mW cm−2 power density at 850 °C, which is a promising result. |
| Keywords | Mn-rich layered perovskites; Physicochemical properties; Cathode materials; SOFC; Symmetrical SOFC |
| Remark |
https://doi.org/10.1016/j.ijhydene.2019.08.254 Link |
ID=543
Simultaneous CO2 and O2 separation coupled to oxy-dry reforming of CH4 by means of a ceramic-carbonate membrane reactor for in situ syngas production
| Authors |
|
| Source |
Chemical Engineering Science
Volume: 210
Time of Publication: 2019
|
| Abstract | It is reported the use of a ceramic-carbonate membrane exhibiting CO2 and O2 permeation, coupled with the oxy-carbon dioxide reforming of methane to produce syngas in a membrane reactor arrangement. The studied membrane is made of a porous fluorite/perovskite mixed conducting ceramic infiltrated with molten carbonates. The CO2 and O2 gas mixture used to perform the oxy-dry reforming process is the membrane’s permeate, which reacts with CH4 supplied in the sweep gas with the assistance of a catalyst. The reactor converts from 74 to 99% of CH4 under the studied separation and reaction conditions. The total rate of syngas production reaches 6.25 mL∙min−1∙cm−2 at 875 °C and a H2/CO ratio ranging from 2.1 to 1.3 between 800 and 875 °C. A long-term test shows a stable performance for 300 h. This work suggests the feasibility of this capture-conversion concept for the valorization of CO2 by the efficient production of syngas. |
| Keywords | Inorganic membrane; Gas permeation; Ceramic-carbonate membrane; Oxy-CO2 reforming of methane; Syngas production |
| Remark |
https://doi.org/10.1016/j.ces.2019.115250 Link |
ID=530
Surface Reconstruction under the Exposure of Electric Fields Enhances the Reactivity of Donor-Doped SrTiO3
| Authors |
|
| Source |
J. Phys. Chem. C
Volume: 123,
Issue: 27,
Pages: 16883-16892 Time of Publication: 2019 |
| Abstract | In the present work, we show how exposure to electric fields during a high-temperature treatment can be used to manipulate surface properties of donor-doped ceramics and thus improve their reactivity. La0.1Sr0.9TiO3 (LSTO) nanoparticles, prepared by hydrothermal synthesis, were consolidated under air with and without external electric fields. Although neither approaches caused grain growth upon consolidation, the treatment under the influence of the electric field (i.e., flash sintering) remarkably enhanced the segregation of Sr on the material’s surface. In addition, a high concentration of O– defects both in bulk as well as on the material surface was demonstrated by spectroscopic methods. This enhanced defect concentration along with the nanoscopic grain size of the field-consolidated materials is probably one of the triggering factors of their improved charge carrier mobility, as observed by impedance spectroscopy. The effect of such a perturbed defect structure on the reactivity of the materials was evaluated by the total oxidation of methane. For materials treated under the influence of electric fields, the catalytic reaction rate improved by a factor of 3 with respect to that of conventionally treated LSTO, along with a remarkable decrease of the activation energy. Thus, electric-field-assisted processes, usually known for their energy-saving character, can also be deemed as an attractive, forward-looking strategy for improving functional properties of ceramics. |
| Remark | Link |
ID=513
Template-free mesoporous La0.3Sr0.7Ti1-xFexO3±δ for CH4 and CO oxidation catalysis
| Authors |
|
| Source |
Applied catalysis B: Enviromental
Volume: 245,
Pages: 536-545 Time of Publication: 2019 |
| Abstract | The design of perovskite oxides with improved textural properties in combination with tunable composition variations is a forward-looking strategy for the preparation of next generation catalytic converter. In the present work we report the template-free synthesis of mesoporous solid solutions of La0.3Sr0.7Ti1-xFexO3±δ (0 ≤ x ≤ 0.5) and the study of their catalytic performance towards CH4 and CO oxidation. Using an innovative polymer complex route, phase pure perovskite solid solutions with specific surface area of 65 m2 g−1 and average pore size of 15 nm were prepared. The iron concentration increase led to a progressive enhancement of not only both concentration and transport of the charge carriers but also reducibility and oxygen desorption capability on the catalyst. As a result, we observed almost complete conversion of CH4 and CO at 600 °C and 300 °C, respectively. Kinetic studies on methane oxidation showed that competing suprafacial and intrafacial reaction mechanisms coexist, and that the concentration of 30% of Fe maximizes the suprafacial contribution. Under reducing conditions at 600 °C the materials retained their structural and morphological integrity, showing superior stability. Finally, the reaction rate of CH4 and CO conversion evidenced that our systems are by a maximum of 90 times more performing than other bulk and nanoporous Fe-based perovskites in literature (e.g. La0.66Sr0.34Co0.2Fe0.8O3-δ), as a result their large surface area, intimate gas-solid contact and short intragrain oxygen diffusion pathways induced by the mesoporous structure. |
| Remark | Link |
ID=499
Invistigation of the role of gravitational attraction in the structure and the catalysis of the formation of particles and study of the catalytic hydrogenation of CO2 using supported ruthenium catalysts on different substrates
| Author |
|
| Source |
Time of Publication: 2018
|
| Remark |
Dissertation o obtain the Degree of Doctor of the University of Patras Link |
ID=498
Investiagation of the role of gravitational attraction in the structure and the catalysis of the formation of particles and study of catalytic hydrogenation of CO2 using supported ruthenium catalysts on different substrates
| Author |
|
| Source |
Time of Publication: 2018
|
| Remark | Link |
ID=490
Wide bandgap oxides for low-temperature single-layered nanocomposite fuel cell
| Authors |
|
| Source |
Nano Energy
Volume: 53,
Pages: 391-397 Time of Publication: 2018 |
| Abstract | A composite of wide bandgap lithium-nickel-zinc-oxide (LNZ) and gadolinium-doped-cerium-oxide (GDC) was systematically analyzed for a low-temperature nanocomposite fuel cell in a so-called single-component configuration in which the electrodes and electrolyte form a homogenous mixture. We found that the operational principle of a single-layer fuel cell can be explained by electronic blocking by the oxide mixture with almost insulator-like properties in the operating voltage regime of the fuel cell, which will prevent short-circuiting, and by its catalytic properties that drive the fuel cell HOR and ORR reactions. The resistance to charge transport and leakage currents are dominant performance limiting factors of the single-component fuel cell. A test cell with Au as current collector reached a power density of 357 mWcm−2 at 550 °C. Changing the current collector to a Ni0.8Co0.15Al0.05LiO2 (NCAL) coated Ni foam produced 801 mWcm−2, explained by better catalytic properties. However, utilizing NCAL coated Ni foam may actually turn the 1-layer fuel cell device into a traditional 3-layer (anode-electrolyte-cathode) structure. This work will help in improving the understanding of the underlying mechanisms of a single-layer fuel cell device important to further develop this potential energy technology. |
| Keywords | Bandgap; Ceramic; Fuel cell; Ionic conductivity; Nanocomposite; Single-component |
| Remark |
https://doi.org/10.1016/j.nanoen.2018.08.070 Link |
ID=485
A novel anode for solid oxide fuel cells prepared from phase conversion of La0.3Sr0.7Fe0.7Cr0.3O3-δ perovskite under humid hydrogen
| Authors |
|
| Source |
Electrochimica Acta
Volume: 284,
Pages: 303-313 Time of Publication: 2018 |
| Abstract | A novel anode for solid oxide fuel cells (SOFCs), consisting of a Ruddlesden-Popper compound, La0.6Sr1.4Fe0.4Cr0.6O3.8, with in situ exsolved α-Fe nanoparticles (RP-LSF + Fe), is prepared from the phase conversion of the La0.3Sr0.7Fe0.7Cr0.3O3-δ (LSFCr-3) perovskite under humid H2 at 800 °C. On the surface of the RP-LSF + Fe anode, Fe cations are presented to be a mixture of Fe2+ and Fe3+, of which the average valence is lower than that in the bulk (Fe3+). The coverage of atomic hydrogen on the RP-LSF + Fe anode is over 0.8 in the pH2 range of 0.017–0.27 atm, implying a significant effect of these small amount (∼8 mol% on the surface) of exsolved Fe nanoparticles (∼200–300 nm) on promoting the dissociative absorption of H2. The charge transfer resistance is found to be closely related to the concentration of surface oxygen vacancies of the oxide matrix. The addition of catalytic amount of Ni (1–3 wt.%) greatly improves the fuel flexibility of the RP-LSF + Fe anode. Furthermore, it contributes to acceleration the phase conversion of the LSFCr-3 perovskite and reduced time for in situ preparation of the RP-LSF + Fe anode. The RP-LSF + Fe anode with 2.7 wt.% Ni exhibits a stable cell performance under 2.7%H2O+1:1-(H2:CO) and 2.7%H2O + CH4 for ∼30 h. It costs shortest time (30 h) to reach a stable cell voltage of 0.76 V at a galvanostatic current density of 0.25 A/cm2 under humid H2, which is clearly an active and stable anode material for SOFCs. |
| Keywords | Solid oxide fuel cell, Oxide anode, Phase conversion, Electrodics, Fuel flexibility |
| Remark |
https://doi.org/10.1016/j.electacta.2018.07.132 Link |
ID=467
Electrochemical promotion of nanodispersed Ru-Co catalysts for the hydrogenation of CO2
| Authors |
|
| Source |
Applied Catalysis B: Environmental
Volume: 232,
Pages: 60-68 Time of Publication: 2018 |
| Abstract | Electrochemical promotion of the CO2 hydrogenation to CH4 and CO on a nanodispersed Ru-Co catalyst has been achieved via slurry deposition of the nanodispersed catalyst on an interlayer Ru film deposited on a BZY (BaZr0.85Y0.15O3) proton conducting solid electrolyte disc. The effect of current is nonFaradaic, with Faradaic efficiency values as high as 60 and leads to a reversible variation of the selectivity to CH4 between 16% and 41%. Due to thermal spillover of protons on the Ru-Co catalyst surface, the open circuit selectivity to CO is quite high, i.e. up to 84% and similar values are obtained via negative potential application, i.e. proton supply to the Ru catalyst film deposited on BZY before the deposition of the nanodispersed catalyst. These results underline the similarity between electrochemical promotion and metal support interactions when using proton conducting supports. They also show the usefulness of electrochemical promotion for mechanistic investigations. The electrochemical promotion of nanodispersed catalysts is a promising step for the practical utilization of electrochemical promotion. |
| Keywords | Electrochemical promotion, EPOC, NEMCA effect, CO2 hydrogenation, Dispersed catalyst, BZY |
| Remark |
https://doi.org/10.1016/j.apcatb.2018.03.031 Link |
ID=462
Amorphous-cathode-route towards low temperature SOFC
| Authors |
|
| Source |
Volume: 2,
Pages: 862-875 Time of Publication: 2018 |
| Abstract | Lowering the operating temperature of solid oxide fuel cell (SOFC) devices is one of the major challenges limiting the industrial breakthrough of this technology. In this study we explore a novel approach to electrode preparation employing amorphous cathode materials. La0.8Sr0.2CoO3−δ dense films have been deposited at different temperatures using pulsed laser deposition on silicon substrates. Depending on the deposition temperature, textured polycrystalline or amorphous films have been obtained. Isotope exchange depth profiling experiments reveal that the oxygen diffusion coefficient of the amorphous film increased more than four times with respect to the crystalline materials and was accompanied by an increase of the surface exchange coefficient. No differences in the surface chemical composition between amorphous and crystalline samples were observed. Remarkably, even if the electronic conductivities measured by the Van Der Pauw method indicate that the conductivity of the amorphous material was reduced, the overall catalytic properties of the cathode itself were not affected. This finding suggests that the rate limiting step is the oxygen mobility and that the local electronic conductivity in the amorphous cathode surface is enough to preserve its catalytic properties. Different cathode materials have also been tested to prove the more general applicability of the amorphous-cathode route. |
| Remark |
DOI: 10.1039/C7SE00606C Link |
ID=440
Surface Protonics Promotes Catalysis
| Authors |
|
| Source |
Nature Scientific Reports 6
Time of Publication: 2016
|
| Abstract | Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics. |
| Remark |
doi:10.1038/srep38007 Link |
ID=438
Comparative study of the electrochemical promotion of CO2 hydrogenation on Ru using Na+, K+, H+ and O2 − conducting solid electrolytes
| Authors |
|
| Source |
Surface Science
Volume: 646,
Pages: 194-203 Time of Publication: 2016 |
| Abstract | The kinetics and the electrochemical promotion of the hydrogenation of CO2 to CH4 and CO are compared for Ru porous catalyst films deposited on Na+, K+, H+ and O2 − conducting solid electrolyte supports. It is found that in all four cases increasing catalyst potential and work function enhances the methanation rate and selectivity. Also in all four cases the rate is positive order in H2 and exhibits a maximum with respect to CO2. At the same time the reverse water gas shift reaction (RWGS) which occurs in parallel exhibits a maximum with increasing and is positive order in CO2. Also in all cases the selectivity to CH4 increases with increasing and decreases with increasing . These results provide a lucid demonstration of the rules of chemical and electrochemical promotion which imply that (∂r/∂Φ)(∂r/∂pD) > 0 and (∂r/∂Φ)(∂r/∂pA) < 0, where r denotes a catalytic rate, Φ is the catalyst work function and pD and pA denote the electron donor and electron acceptor reactant partial pressures respectively. |
| Keywords | Electrochemical promotion of catalysis, Ion conducting support, Hydrogenation of CO2, Ruthenium catalyst, Rules of promotion, Metal–support interactions |
| Remark |
https://doi.org/10.1016/j.susc.2015.09.011 Link |
ID=432
Microstructural engineering and use of efficient poison resistant Au-doped Ni-GDC ultrathin anodes in methane-fed solid oxide fuel cells
| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 43,
Issue: 2,
Pages: 885–893 Time of Publication: 2018 |
| Abstract | Ultrathin porous solid oxide fuel cell (SOFC) anodes consisting of nickel-gadolinia-doped-ceria (Ni-GDC) cermets with a unique porous micro-columnar architecture with intimate contact between the GDC and the Ni phases were made by magnetron sputtering at an oblique deposition angle and characterised in detail by a variety of methods prior to use in hydrogen or methane-fuelled SOFCs. These Ni-GDC anodes exhibited excellent transport properties, were robust under thermal cycling and resistant to delamination from the underlying yttria-stabilised zirconia electrolyte. Similarly prepared Au-doped Ni-GDC anodes exhibited the same morphology, porosity and durability. The gold associated exclusively with the Ni component in which it was present as a surface alloy. Strikingly, whatever their treatment, a substantial amount of Ce3+ persisted in the anodes, even after operation at 800 °C under fuel cell conditions. With hydrogen as fuel, the un-doped and Au-doped Ni-GDC anodes exhibited identical electrochemical performances, comparable to that of much thicker commercial state-of-the-art Ni-GDC anodes. However, under steam reforming conditions with CH4/H2O mixtures the behaviour of the Au-doped Ni-GDC anodes were far superior, exhibiting retention of good power density and dramatically improved resistance to deactivation by carbon deposition. Thus two distinct beneficial effects contributed to overall performance: persistence of Ce3+ in the working anodes could induce a strong metal-support interaction with Ni that enhanced the catalytic oxidation of methane, while formation of a Nisingle bondAu surface alloy that inhibited carbonisation and poisoning of the active nickel surface. |
| Keywords | SOFC; Ultrathin film anodes; Magnetron sputtering; Gadolinia doped ceria; Carbon-tolerant; Gold doping |
| Remark |
https://doi.org/10.1016/j.ijhydene.2017.11.020 Link |
ID=403
Composite mixed ionic-electronic conducting ceramic for intermediate temperature oxygen transport membrane
| Authors |
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| Source |
Ceramics International
Volume: 43,
Issue: 1,
Pages: S628-S632 Time of Publication: 2017 |
| Abstract | The dense ceramic substrate formed by a mixed ionic-electronic conducting (MIEC) material can be used as an oxygen transport membrane (OTM), enabling the transport of high flux oxygen with certain selectivity and gas separation at high temperatures (800 ~ 900 °C). In recent years, Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) has been reported to be a promising MIEC material for oxygen permeation due to its relatively high oxygen ion conductivity at high temperatures. However, the catalytic efficiency of BSCF is relatively low among the MIEC materials, resulting in the dramatic decrease of oxygen permeation at temperatures below 800 °C. In the present study, a composite MIEC ceramic consisting of a BSCF substrate and the catalytic La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) layer has been proposed. A simple method of laser surface melting is executed to fabricate the composite oxygen transport membrane. The scanning electron microscope (SEM) investigations show that LSCF powders can be well-adherent to the BSCF surface after laser scanning melting process. The oxygen permeation flux reaches 0.5 ml min−1 cm−2 for pure BSCF membrane with thickness of 420 µm, while the BSCF membrane substrate with laser scanning LSCF exhibits substantial improvement on oxygen permeation up to 60% at 700 °C. The result suggests that the composite MIEC ceramic has significant potential for intermediate temperature oxygen transport membrane. |
| Keywords | Membranes, Composites, Laser surface melting |
| Remark |
https://doi.org/10.1016/j.ceramint.2017.05.222 Link |
ID=395
Effect of Pt catalyst and external circuit on the hydrogen permeation of Mo and Nb co-doped lanthanum tungstate
| Authors |
|
| Source |
Journal of Membrane Science
Volume: 553,
Pages: 336–341 Time of Publication: 2017 |
| Abstract | In this contribution, the hydrogen permeation properties of 30% Mo and 15% Nb co-doped La5.4WO11.1-δ (LWNM30) with/without Pt catalyst and external circuit were investigated. It was found that the surface reaction was the limiting factor in the hydrogen permeation process of LWNM30, and could be improved by using Pt as catalyst. The applied external circuit could also increase the hydrogen flux of LWNM30, and two followed effects might be responsible: the external circuit could transfer the electrons and promote the diffusion process; the external circuit could remove the charge layer on the surface and enhance the surface reaction rate. |
| Keywords | Lanthanum tungstate; Hydrogen permeation; Pt catalyst; Mo and Nb; External circuit |
| Remark | Link |
ID=391
Surface Protonics Promotes Catalysis
| Authors |
|
| Source |
Nature Scientific Reports
Volume: 6,
Pages: Article number: 38007 Time of Publication: 2016 |
| Abstract | Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics. |
| Keywords | Catalytic mechanisms, Energy, Heterogeneous catalysis, Surface spectroscopy |
| Remark |
doi:10.1038/srep38007 Link |
ID=352
Direct conversion of methane to aromatics in a catalytic co-ionic membrane reactor
| Authors |
|
| Source |
Science
Volume: 353,
Issue: 6299,
Pages: 563-566 Publisher: American Association for the Advancement of Science (AAAS), ISBN: Print ISSN:0036-8075 Online ISSN:1095-9203, Time of Publication: 2016-08 |
| Abstract | Nonoxidative methane dehydroaromatization (MDA: 6CH4 ↔ C6H6 + 9H2) using shape-selective Mo/zeolite catalysts is a key technology for exploitation of stranded natural gas reserves by direct conversion into transportable liquids. However, this reaction faces two major issues: The one-pass conversion is limited by thermodynamics, and the catalyst deactivates quickly through kinetically favored formation of coke. We show that integration of an electrochemical BaZrO3-based membrane exhibiting both proton and oxide ion conductivity into an MDA reactor gives rise to high aromatic yields and improved catalyst stability. These effects originate from the simultaneous extraction of hydrogen and distributed injection of oxide ions along the reactor length. Further, we demonstrate that the electrochemical co-ionic membrane reactor enables high carbon efficiencies (up to 80%) that improve the technoeconomic process viability. Methane gas is expensive to ship. It is usually converted into carbon monoxide and hydrogen and then liquefied. This is economically feasible only on very large scales. Hence, methane produced in small amounts at remote locations is either burned or not extracted. A promising alternative is conversion to benzene and hydrogen with molybdenumzeolite catalysts. Unfortunately, these catalysts deactivate because of carbon buildup; plus, hydrogen has to be removed to drive the reaction forward. Morejudo et al. address both of these problems with a solid-state BaZrO3 membrane reactor that electrochemically removes hydrogen and supplies oxygen to suppress carbon buildup. |
| Keywords | CMR, MDA, catalytic membrane reactor, ZSM-5, MCM-22, FBR, FBR-PolyM, Pd-CMR, Co-ionic CMR, FT, ProboStat CMR base unit (NORECS) |
| Remark |
http://science.sciencemag.org/highwire/filestream/682540/field_highwire_adjunct_files/0/Morejudo.SM.pdf BaZrO3 BaZrO3 Link |
ID=349
Synthesis and characterization of robust, mesoporous electrodes for solid oxide fuel cells
| Authors |
|
| Source |
Journal of Materials Chemistry A
Time of Publication: 2016
|
| Abstract | The use of mesoporous electrodes in solid oxide cells would lead to a significant enhancement of the performance due to their high surface area and large number of active sites for electrochemical reactions. However, their application in real devices is still hindered by the potential instability of the mesostructure and morphology at high temperatures required for device fabrication and under severe conditions for high-current, long-term operation. Here we report our findings on the preparation and characterization of mesoporous electrodes based on ceria infiltrated with catalysts: an anode consisting of a Ce0.8Sm0.2O1.9 (SDC) scaffold infiltrated with Ni and a cathode consisting of an SDC scaffold infiltrated with Sm0.5Sr0.5CoO3−δ (SSC). In particular, a doped-zirconia electrolyte supported cell with a mesoporous Ni–SDC anode and a mesoporous SSC–SDC cathode demonstrates an excellent peak power density of 565 mW cm−2 at 750 °C (using humidified hydrogen as the fuel). More importantly, both mesoporous electrodes display remarkable stability, yielding a combined electrode virtual non-degradation for the last 500 hours of the test at a constant current density of 635 mA cm−2 at 750 °C, demonstrating the potential of these mesoporous materials as robust electrodes for solid oxide fuel cells or other high-temperature electrochemical energy storage and conversion devices. |
| Remark |
DOI: 10.1039/C6TA00321D Link |
ID=337
Synthesis and properties of La0.05Ba0.95Ti1 −xMyO3 (M = Mn, Ce) as anode materials for solid oxide fuel cells
| Authors |
|
| Source |
Solid State Ionics
Volume: 283,
Pages: 21–29 Time of Publication: 2015 |
| Abstract | Stoichiometric and sub-stoichiometric lanthanum barium titanates (LBT) of perovskite structure type, substituted or not with Mn and/or Ce at the Ti-site, were prepared by sol–gel route with heat treatment in air. All the compounds display a cubic Pm-3m symmetry, which remains stable in reducing atmosphere. Whereas Mn substitution highly promotes the reducibility of the material, the electrical and electrochemical performance of Mn-doped compounds is decreased with respect to non-doped sub-stoichiometric LBT. In contrast, the electrical conductivity and resistance polarization of Ce-substituted LBT are close to those of non-doped LBT and Ce-substituted LBT appears especially efficient in improving the catalytic properties for methane steam reforming and avoiding carbon formation. |
| Keywords | SOFC; Anode; Perovskite; Barium titanate; Impedance electrochemical spectroscopy; Methane steam reforming |
| Remark |
doi:10.1016/j.ssi.2015.11.005 Link |
ID=336
Molybdenum doped Pr0.5Ba0.5MnO3−δ (Mo-PBMO) double perovskite as a potential solid oxide fuel cell anode material
| Authors |
|
| Source |
Journal of Power Sources
Volume: 301,
Pages: 237–241 Time of Publication: 2016 |
| Abstract | A layered Mo doped Pr0.5Ba0.5MnO3−δ (Mo-PBMO) double perovskite oxide was prepared by a modified sol–gel method and the properties of the fabricated material are characterized by various technologies. The results of X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), and thermogravimetric analysis (TGA) demonstrate that the treatment in reducing atmosphere at high temperature lead to a significant phase transformation of the material to a single cubic phase as well as with the Mo in multiple oxidized states. Such character leads to the production of large amount of oxygen deficiency with facilitated oxygen diffusion. The electrochemical performance tests of half-cell and single cell SOFCs exhibit the promoted effect of Mo on catalytic activity for the oxidation of H2 and CH4, indicating that Mo-PBMO could serve as an anode material candidate for SOFCs. |
| Keywords | Mo; Pr0.5Ba0.5MnO3−δ; Double perovskite; Anode; SOFC |
| Remark |
doi:10.1016/j.jpowsour.2015.09.127 Link |
ID=332
Exceptional hydrogen permeation of all-ceramic composite robust membranes based on BaCe0.65Zr0.20Y0.15O3−δ and Y- or Gd-doped ceria
| Authors |
|
| Source |
Energy Environ. Sci.
Volume: 8,
Pages: 3675-3686 Time of Publication: 2015 |
| Abstract | Mixed proton and electron conductor ceramic composites were examined as hydrogen separation membranes at moderate temperatures (higher than 500 °C). In particular, dense ceramic composites of BaCe0.65Zr0.20Y0.15O3−δ (BCZ20Y15) and Ce0.85M0.15O2−δ (M = Y and Gd, hereafter referred to as YDC15 and GDC15), as protonic and electronic conducting phases respectively, were successfully prepared and tested as hydrogen separation membranes. The mixture of these oxides improved both chemical and mechanical stability and increased the electronic conductivity in dual-phase ceramic membranes. The synthetic method and sintering conditions were optimized to obtain dense and crack free symmetric membranes. The addition of ZnO as a sintering aid allowed achieving robust and dense composites with homogeneous grain distribution. The chemical compatibility between the precursors and the influence of membrane composition on electrical properties and H2 permeability performances were thoroughly investigated. The highest permeation flux was attained for the 50 : 50 volume ratio BCZ20Y15–GDC15 membrane when the feed and the sweep sides of the membrane were hydrated, reaching values of 0.27 mL min−1 cm−2 at 755 °C on a 0.65 mm thick membrane sample, currently one of the highest H2 fluxes obtained for bulk mixed protonic–electronic membranes. Increasing the temperature to 1040 °C, increased the hydrogen flux up to 2.40 mL min−1 cm−2 when only the sweep side was hydrated. The H2 separation process is attributed to two cooperative mechanisms, i.e. proton transport through the membrane and H2 production via the water splitting reaction coupled with oxygen ion transport. Moreover, these composite systems demonstrated a very good chemical stability under a CO2-rich atmosphere such as catalytic reactors for hydrogen generation. |
| Remark |
DOI: 10.1039/C5EE01793A Link |
ID=328
Comparative study of the electrochemical promotion of CO2 hydrogenation on Ru using Na+, K+, H+ and O2 − conducting solid electrolytes
| Authors |
|
| Source |
Surface Science
Time of Publication: 2015
|
| Abstract | The kinetics and the electrochemical promotion of the hydrogenation of CO2 to CH4 and CO are compared for Ru porous catalyst films deposited on Na+, K+, H+ and O2 − conducting solid electrolyte supports. It is found that in all four cases increasing catalyst potential and work function enhances the methanation rate and selectivity. Also in all four cases the rate is positive order in H2 and exhibits a maximum with respect to CO2. At the same time the reverse water gas shift reaction (RWGS) which occurs in parallel exhibits a maximum with increasing pH2pH2 and is positive order in CO2. Also in all cases the selectivity to CH4 increases with increasing pH2pH2 and decreases with increasing pCO2pCO2. These results provide a lucid demonstration of the rules of chemical and electrochemical promotion which imply that (∂r/∂Φ)(∂r/∂pD) > 0 and (∂r/∂Φ)(∂r/∂pA) < 0, where r denotes a catalytic rate, Φ is the catalyst work function and pD and pA denote the electron donor and electron acceptor reactant partial pressures respectively. |
| Keywords | Effect of Ru catalyst support and potential on product selectivity. |
| Remark |
In Press, doi:10.1016/j.susc.2015.09.011 Link |
ID=327
Electrochemical promotion of the hydrogenation of CO2 on Ru deposited on a BZY proton conductor
| Authors |
|
| Source |
Journal of Catalysis
Volume: 331,
Pages: 98–109 Time of Publication: 2015 |
| Abstract | he kinetics and the electrochemical promotion of the hydrogenation of CO2 on polycrystalline Ru deposited on BZY (BaZr0.85Y0.15O3−α + 1 wt% NiO), a proton conductor in wet atmospheres, with α ≈ 0.075, was investigated at temperatures 300–450 °C and atmospheric pressure. Methane and CO were the only detectable products and the selectivity to CH4 could be reversibly controlled between 15% and 65% by varying the catalyst potential by less than 1.2 V. The rate and the selectivity to CH4 are very significantly enhanced by proton removal from the catalyst via electrochemically controlled spillover of atomic H from the catalyst surface to the proton-conducting support. The effect is strongly non-Faradaic and the apparent Faradaic efficiency of methanation takes values up to 500 and depends strongly on the porous Ru catalyst film thickness. The observed strong promotional effect, in conjunction with the observed reaction kinetics, is in good agreement with the rules of electrochemical and chemical promotion. |
| Keywords | Hydrogenation of CO2; CO2 methanation; Ru catalyst; RWGS reaction; BZY proton conducting support; Selectivity modification; Electrochemical promotion of catalysis (EPOC); Non-faradaic electrochemical modification of catalytic activity (NEMCA effect) |
| Remark |
doi:10.1016/j.jcat.2015.08.023 Link |
ID=326
Electrochemical Promotion of Ir0.5Pt0.5O2/YSZ
| Authors |
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| Source |
Topics in Catalysis
Volume: 58,
Issue: 18,
Pages: 1270-1275 Time of Publication: 2015 |
| Abstract | A high surface area, nanostructured bimetallic oxide catalyst, Ir0.5Pt0.5O2, deposited on YSZ was studied for the electrochemical promotion of ethylene oxidation. The catalyst was synthesized using the modified Adams fusion method and was characterized regarding its structure, morphology and specific surface area via XPS, XRD, HRTEM, SEM and BET. Regarding the performance for electrochemical promotion, it was found that the rate of ethylene oxidation can be enhanced significantly and in a strongly non-faradaic manner via positive potential application, exhibiting strongly electrophobic behaviour. |
| Keywords | Electrochemical promotion, EPOC, Ir0.5Pt0.5O2, Adams fusion method |
| Remark | Link |
ID=324
Development of a Coking-Resistant NiSn Anode for the Direct Methane SOFC
| Authors |
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| Source |
Fuel Cells
Volume: 15,
Issue: 5,
Pages: 711–717 |
| Abstract | The present work reports on the development of a coking-resistant NiSn-based membrane electrode assembly (MEA) for internal CH4 reforming in solid oxide fuel cells (SOFCs). Catalyst powder was prepared in a centrifugal casting oven by melting stoichiometric amounts of Ni and Sn under vacuum. The formation of Ni3Sn2 intermetallic phase was confirmed by XRD analysis. Catalytic activity for CH4 reforming and stability of the NiSn powder were first evaluated in a quartz glass reactor for 4 h at 600–1,000 °C. The main reaction products H2 and CO were detected by gas chromatography while no carbon formation was detected during the experiments. Then, 3YSZ electrolyte-supported MEAs were fabricated with a Ni3Sn2/YSZ anode and LSM/YSZ cathode and characterized under SOFC conditions. The MEA showed an excellent stability under CH4 atmosphere (3% H2O) at 850 °C over more than 650 h. No substantial decrease in cell potential was observed during this period. |
| Keywords | Anode Material;Intermetallic Phase;Internal Reforming;Methane;Nickel-Tin Alloy;Ni3Sn2;SOFC;Solid Oxide Fuel Cell |
| Remark |
DOI: 10.1002/fuce.201400187 Link |
ID=313
Praseodymium-deficiency Pr0.94BaCo2O6-δ double perovskite: A promising high performance cathode material for intermediate-temperature solid oxide fuel cells
| Authors |
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| Source |
Journal of Power Sources
Volume: 239,
Pages: 741–750 Time of Publication: 2015 |
| Abstract | Praseodymium-deficiency Pr0.94BaCo2O6-δ (P0.94BCO) double perovskite has been evaluated as a cathode material for intermediate-temperature solid oxide fuel cells. X-ray diffraction pattern shows the orthorhombic structure with double lattice parameters from the primitive perovskite cell in Pmmm space group. P0.94BCO has a good chemical compatibility with Ce0.9Gd0.1O1.95 (CGO) electrolyte even at 1000 °C for 24 h. It is observed that the Pr-deficiency can introduce the extra oxygen vacancies in P0.94BCO, further enhancing its electrocatalytic activity for oxygen reduction reaction. P0.94BCO demonstrates the promising cathode performance as evidenced by low polarization are-specific resistance (ASR), e. g. 0.11 Ω cm2 and low cathodic overpotential e. g. −56 mV at a current density of −78 mA cm−2 at 600 °C in air. These features are comparable to those of the benchmark cathode Ba0.5Sr0.5Co0.8Fe0.2O3-δ. The fuel cell CGO-Ni|CGO|P0.94BCO presents the attractive peak power density of 1.05 W cm−2 at 600 °C. Furthermore, the oxygen reduction kinetics of P0.94BCO material is also investigated, and the rate-limiting steps for oxygen reduction reaction are determined. |
| Keywords | Intermediate-temperature solid oxide fuel cell; Cathode material; Double perovskite; Electrochemical performance; Oxygen reduction reaction |
| Remark |
doi:10.1016/j.jpowsour.2015.06.007 Link |
ID=310
Triode operation for enhancing the performance of H2S-poisoned SOFCs operated under CH4–H2O mixtures
| Authors |
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| Source |
Solid State Ionics
Volume: 277,
Pages: 65–71 Time of Publication: 2015 |
| Abstract | Performances of Solid Oxide Fuel Cells (SOFCs) were investigated in triode operation mode under methane steam reforming in the presence of H2S. Both the catalytic performances for methane steam reforming and the electrochemical properties for the electrochemical oxidation of hydrogen of a Ni/GDC anode drastically dropped in the presence of 1 ppm H2S. Poisoned catalytic sites are different from those for the hydrogen electrochemical oxidation. Triode operation, i.e. application of moderate negative currents between the anode and an auxiliary electrode, can improve electrochemical properties, as a result of a local production of H2 coming from H2O electrolysis. Some specific triode operations were found to achieve a thermodynamic efficiency close to the unity to avoid any energy overconsumption. |
| Keywords | SOFC; Triode operation; H2S poisoning; Ni/GDC anode |
| Remark |
doi:10.1016/j.ssi.2015.05.003 Link |
ID=294
Hydrogen separation membranes based on dense ceramic composites in the La27W5O55.5–LaCrO3 system
| Authors |
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| Source |
Journal of Membrane Science
Volume: 479,
Pages: 39–45 Time of Publication: 2015 |
| Abstract | Some compositions of ceramic hydrogen permeable membranes are promising for integration in high temperature processes such as steam methane reforming due to their high chemical stability in large chemical gradients and CO2 containing atmospheres. In the present work, we investigate the hydrogen permeability of densely sintered ceramic composites (cercer) of two mixed ionic-electronic conductors: La27W3.5Mo1.5O55.5−δ (LWM) containing 30, 40 and 50 wt% La0.87Sr0.13CrO3−δ (LSC). Hydrogen permeation was characterized as a function of temperature, feed side hydrogen partial pressure (0.1–0.9 bar) with wet and dry sweep gas. In order to assess potentially limiting surface kinetics, measurements were also carried out after applying a catalytic Pt-coating to the feed and sweep side surfaces. The apparent hydrogen permeability, with contribution from both H2 permeation and water splitting on the sweep side, was highest for LWM70-LSC30 with both wet and dry sweep gas. The Pt-coating further enhances the apparent H2 permeability, particularly at lower temperatures. The apparent H2 permeability at 700 °C in wet 50% H2 was 1.1×10−3 mL min−1 cm−1 with wet sweep gas, which is higher than for the pure LWM material. The present work demonstrates that designing dual-phase ceramic composites of mixed ionic-electronic conductors is a promising strategy for enhancing the ambipolar conductivity and gas permeability of dense ceramic membranes. |
| Keywords | Hydrogen separation; Dense ceramic membrane; Ceramic–ceramic composite; Lanthanum tungstate; Lanthanum chromite |
| Remark |
doi:10.1016/j.memsci.2015.01.027 Link |
ID=289
Pure and Mn-doped La4SrTi5O17 layered perovskite as potential solid oxide fuel cell material: Structure and anodic performance
| Authors |
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| Source |
Journal of Power Sources
Volume: 274,
Pages: 806–815 Time of Publication: 2015 |
| Abstract | Pure and 5% Mn doped layered perovskites La4SrTi5O17, members of the La4Srn-4(Ti,Mn)nO3n+2 series with n = 5, have been synthesized and investigated as anode materials for Solid Oxide Fuel Cells. The use of XRD, neutron and electron diffraction techniques allows clarifying some divergences concerning the structural characterization within the family, not only in air but also in anodic-like N2/H2(97/3) atmosphere. The electrical conductivity of both compounds is very low in air but those values increase by two orders of magnitude in diluted hydrogen. The study of catalytic properties for methane steam reforming as well as in-depth analysis of the SOFC anodic behaviour of both materials are described, for which a microstructure optimization of the electrode allows to demonstrate the potential interest of the lamellar materials upon the classical three-dimensional cubic-like LSTs. |
| Keywords | SOFC; Anode; Layered perovskite; Titanate; Methane steam reforming; Electrochemical impedance spectroscopy |
| Remark |
doi:10.1016/j.jpowsour.2014.10.131 Link |
ID=288
Electrochemical performance and carbon deposition resistance of Ce-doped La0.7Sr0.3Fe0.5Cr0.5O3-δ anode materials for solid oxide fuel cells fed with syngas
| Authors |
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| Source |
Journal of Power Sources
Volume: 254,
Pages: 483–487 Time of Publication: 2015 |
| Abstract | Ce-doped La0.7Sr0.3Fe0.5Cr0.5O3-δ (Ce-LSFC) perovskite anode catalysts for solid oxide fuel cells are successfully synthesized by a modified combustion method for the first time. The pure perovskite structure without formation of CeO2 is obtained when the content of Ce ≤ 10%. Compared with La0.7Sr0.3Fe0.5Cr0.5O3-δ anode, Ce-LSFC anode not only shows much higher catalytic activity towards the oxidation of syngas with less carbon deposition, but also displays better regeneration from coking. The enhanced performance is attributed to the more available oxygen vacancies in lattice and better oxygen mobility after doping with Ce. |
| Keywords | SOFC; Ce-doped LSFC; Perovskite |
| Remark |
doi:10.1016/j.jpowsour.2014.10.090 Link |
ID=203
Solid-state photoelectrochemical H2 generation with gaseous reactants
| Authors |
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| Source |
Electrochimica Acta
Volume: 97,
Pages: 320–325 Time of Publication: 2013-05 |
| Abstract | Photocurrent and H2 production were demonstrated in an all solid-state photoelectrochemical cell employing gaseous methanol and water vapour at the photoanode. Open circuit photovoltage of around -0.4 V and short circuit photocurrent of up to 250 μA/cm2 were obtained. At positive bias, photocurrent generation was limited by the irradiance, i.e., the amount of photogenerated charge carriers at the anode. Time constants and impedance spectra showed an electrochemical capacitance of the cell of about 15 μF/cm2 in the dark, which increased with increasing irradiance. With only water vapour at the anode, the short circuit photocurrent was about 6% of the value with gaseous methanol and water vapour. The photoanode and electrocatalyst on carbon paper support were affixed to the proton conducting membrane using Nafion® as adhesive, an approach that yielded photocurrents up to 15 times better than that of a cell assembled by hot-pressing, in spite of the overall cell resistance of the latter being up to 5 times less than that of the former. This is attributed, at least partially, to reactants being more readily available at the photoanode of the better performing cell. |
| Keywords | |
| Remark | Link |
ID=188
Transient Oxygen Permeation and Surface Catalytic Properties of Lanthanum Cobaltite Membrane under Oxygen–Methane Gradient
| Author |
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| Source |
Ind. Eng. Chem. Res.
Volume: 51,
Issue: 39,
Pages: 12917–12925 Time of Publication: 2012-09 |
| Abstract | Oxygen permeation through mixed-conducting ceramic membranes in an air/methane gradient is important for their applications in membrane reactors for air separation and partial oxidation of hydrocarbons. This study examines transient characteristics of oxygen permeation and surface catalytic properties of La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) membranes in an oxygen/methane gradient for an extended period of time. Upon exposure to an oxygen/methane gradient, the oxygen permeation flux of the membrane increases to a maximum at around 55 h, then decreases and reaches a steady-state value at around 200 h. The maximum and steady-state flux is approximately 60% and 30% higher than the initial flux of the fresh membrane, respectively. The surface catalytic properties of the membrane exposed to methane also change with the exposure time in a similar fashion. However, the apparent activation energy for oxygen permeation for the membranes at various stages of the transient study is nearly constant while the effects of temperature, feed pressure, and sweep flow rate on catalytic properties are also similar for the fresh and aged membranes. The surface of a LSCF membrane reacts with methane resulting in a formation of a thin porous layer which changes the surface catalytic properties. The membrane surface becomes more active for reaction with increased selectivity for carbon monoxide formation upon exposure to methane. This lowers oxygen partial pressure in the permeate side and increases the driving force for oxygen permeation and, therefore, increases oxygen permeation flux. Under the studied experimental conditions the membrane can reach steady-state for continuous operation. |
| Remark | Link |
ID=172
Process and Apparatus of CO2 Energy Source Adopted in Solid Oxide Fuel Cell - CO2 Energy Conversion Cycle
| Authors |
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| Source |
Time of Publication: 2012-05
|
| Abstract | A process and apparatus of “Solid Oxide Fuel Cell (SOFC)-CO2 Energy Conversion Cycle (referred to as SOFC-CO2-ECC)” are invented to adopt CO2 as energy sources from waste/stock gas or convert and fix it in the useful compounds. CO2 is converted into CO and O2 via simultaneously catalytic and electrochemical reactions in SOFC for power generation and CO2 cracking. Furthermore, CO is used either as the fuel in SOFC for power generation or starting materials in the chemical reactors to produce CO-derivatives of energy source materials and useful chemical compounds. Hence, SOFC-CO2-ECC is an active or scientific carbon cycle with zero emission of CO2. Thus, the efficacy of environmental protection via solving the problem of CO2 greenhouse effect is achieved, so as to grasp of the “Right of Carbon Emission Trading” issues. |
| Remark |
United States Patent Application 20120115067 Link |
ID=139
Effects of (LaSr)(CoFeCu)O3-δ Cathodes on the Characteristics of Intermediate Temperature Solid Oxide Fuel Cells
| Authors |
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| Source |
Journal of Power Sources
Volume: 201,
Pages: 18–25 Time of Publication: 2012-03 |
| Abstract | In this study, Cu2+ ions doped La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes are prepared for use in solid oxide fuel cells (SOFCs). The maximum electrical conductivities of the La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ (438 S cm−1) and the La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ (340 S cm−1) discs are higher than that of the La0.6Sr0.4Co0.2Fe0.8O3−δ disc (LSCF; 81 S cm−1) sintered at 1100 °C. The substitution of Cu2+ over Fe3+ leads to a higher coefficients of thermal expansion (CTE), while the replacement of Co3+ by Cu2+ results in a lower CTE. Single cells with the La0.6Sr0.4Co0.2Fe0.8O3−δ, La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ, and La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes operating at 650 °C and 550 °C show similar ohmic resistance (R0) values while the polarization resistance (RP) values of the cells with the La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ and a0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes are slightly lower than that of the single cell with the La0.6Sr0.4Co0.2Fe0.8O3−δ cathode, indicating that the Cu2+-doped LSCF cathode exhibits a greater electrochemical catalytic activity for oxygen reduction. Maximum power densities of the cells with the La0.6Sr0.4Co0.2Fe0.8O3−δ, La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ, and La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes operating at 700 °C read respectively 1.07, 1.15, and 1.24 W cm−2. It is evident that the doping of Cu2+ ions in LSCF is beneficial to the electrochemical performance of the cells. |
| Keywords | Solid oxide fuel cell; cathode; cathode; impedance; Cell performance |
| Remark | Link |
ID=135
Autothermal Reforming of Methane in Proton-Conducting Ceramic Membrane Reactor
| Authors |
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| Source |
Ind. Eng. Chem. Res. Volume: 50, Issue: 22, Pages: 12426–12432 Time of Publication: 2011-10 |
| Abstract | Endothermic steam reforming of methane for hydrogen production requires heat input with selective oxidation of methane. Dense SrCe0.75Zr0.20Tm0.05O3-δ perovskite membranes were combined with a reforming catalyst to demonstrate the feasibility of a heat-exchange membrane reactor for steam reforming of methane coupled with selective oxidation of permeated hydrogen. The reforming catalyst used was a prereduced nickel based catalyst supported on γ-Al2O3. Hydrogen produced via the steam reforming of methane or water gas shift reaction was able to diffuse through the catalyst bed and transport through the membrane. The permeated hydrogen reacted with oxygen (from air) to produce heat for the steam reforming of methane on the other side of the membrane. The membrane reactor avoids the use of an expensive air separation unit to produce pure oxygen. The influence of experimental conditions, such as temperature, gas hourly space velocity, and the steam to carbon (S/C) ratio, on the membrane reactor was investigated. SrCe0.75Zr0.20Tm0.05O3-δ showed good chemical stability in steam reforming conditions as X-ray diffraction analysis of the membrane surface exposed to steam-reforming conditions for 425 h showed only minor CeO2 formation. The experimental data demonstrate the feasibility of using a proton conducting ceramic membrane in the heat-exchange membrane reactor for steam reforming of methane coupled with selective oxidation. |
| Remark | Link |
ID=126
Partial Oxidation of Methane and Oxygen Permeation in SrCoFeOx Membrane Reactor with Different Catalysts
| Author |
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| Source |
Ind. Eng. Chem. Res.
Volume: 50,
Issue: 13,
Pages: 7941–7948 Time of Publication: 2011-05 |
| Abstract | Partial oxidation of methane (CH4) and oxygen permeation in a dense SrCoFeOx disk membrane reactor were studied with the reducing side of the membrane packed with different catalysts (catalyst support γ-Al2O3, La0.6Sr0.4Co0.8Fe0.2O3−δ, and 10 wt % Ni/γ-Al2O3) of increasing reaction activities for CH4 oxidation. The influence of temperature, flow rates, and inlet CH4 concentration (diluted with helium) on the performance of the different membrane reactors was investigated. The oxygen permeation flux and CH4 conversion increased in the following order: γ-Al2O3 < La0.6Sr0.4Co0.8Fe0.2O3−δ < 10% Ni/γ-Al2O3. The membrane reactor with the reforming catalyst of 10 wt % Ni/γ-Al2O3 had the highest CH4 conversion (90%), CO selectivity (97%), and oxygen permeation flux (2.40 mL/(cm2 min)) at 900 °C. The improvement of the oxygen permeation through the membranes with different catalysts emphasizes the effect of the CH4 oxidation reaction rate on the reducing side of the membrane on the oxygen permeation flux through the mixed-conducting ceramic membranes. Under identical conditions, the oxygen permeation flux through mixed-conducting ceramic membrane with a reducing gas is a strong function of the catalytic activity for the oxidation of the reducing gas. |
| Remark | Link |
ID=108
Directed integration of ZnO nanobridge sensors using photolithographically patterned carbonized photoresist
| Authors |
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| Source |
Nanotechnology
Volume: 21,
Issue: 19
Time of Publication: 2010-05
|
| Abstract | A method for achieving large area integration of nanowires into electrically accessible device structures remains a major challenge. We have achieved directed growth and integration of ZnO nanobridge devices using photolithographically patterned carbonized photoresist and vapor transport. This carbonized photoresist method avoids the use of metal catalysts, seed layers, and pick and place processes. Growth and electrical connection take place simultaneously for many devices. Electrical measurements on carbonized photoresist/ZnO nanobridge/carbonized photoresist structures configured as three-terminal field effect devices indicate bottom gate modulation of the conductivity of the n-type ZnO channel. Nanobridge devices were found to perform well as ultraviolet and gas sensors, and were characterized as regards ultraviolet light pulsing, oxygen concentration, and humidity. The sensitivity of the three-terminal nanobridge sensors to UV light and oxygen was enhanced by application of a negative bottom gate voltage. |
