The Experts below are selected from a list of 1065 Experts worldwide ranked by ideXlab platform
Peter Wagner - One of the best experts on this subject based on the ideXlab platform.
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Long-term Operation of High Temperature Polymer Electrolyte Membrane Fuel Cells with Fuel Composition Switching and Oxygen Enrichment†
Fuel Cells, 2018Co-Authors: Francisco Javier Pinar, Alexander Dyck, Maren Rastedt, Peter WagnerAbstract:The performance of commercially available High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) cells was electrochemically (impedance spectroscopy, polarization curves, performance over time) and optically characterized ante and post mortem via micro-computed tomography. Investigations on the performance gain, due to oxygen enrichment of cathode air and the capabilities of the commercial MEAs to switch and operate between pure hydrogen and synthetic dry reformate (78% H2 and 22% CO2), were carried out. Two experiments at constant load conditions were performed, Cycle 1 consisted of 12 h pure hydrogen operation followed by 12 h of synthetic reformate, while Cycle 2 was operated with 1 h of H2 followed by 5 h of synthetic reformate. The results revealed that oxygen enrichment improves mass transport from the gas flow channels to the cathode catalyst layer as well as catalyst utilization. Thus, oxygen concentration increase from 21% (air) to 30% at 0.3 A cm−2 developed a performance improvement of roughly 8%. Only marginally influence on fuel cell performance and degradation was observed in fuel switching experiments. A content of 22% CO2 had little influence on degradation, which could mainly be related to fuel dilution. Besides, micro-computed tomography (µ-CT) investigations revealed similar membrane and catalyst layer degradation for both kinds of fuel switching tests.
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demonstrating feasibility of a high temperature polymer electrolyte membrane fuel cell operation with natural gas reformate composition
International Journal of Hydrogen Energy, 2017Co-Authors: Javier F Pinar, Nadine Pilinski, Maren Rastedt, Peter Wagner, Alexander DyckAbstract:Abstract Experimental data on the performance of a single cell PBI-based HT-PEMFC operated with a fuel composition similar to natural gas reformate and oxygen enriched cathode air are presented. A test studying the effect of CO2, H2O and CO in the fuel on fuel cell performance revealed that the presence of CO2 mainly worsens mass transport, H2O improves proton conduction and CO influences reaction kinetics as well as causing mass transport limitations. A small increase of the O2 concentration in the oxidant provided a boost on performance. Electrical efficiency of the fuel cell was improved from 36.6% with H2/air operation up to 38.2% with synthetic reformate gas/30% O2 enriched air. Three 1000 h long-term tests at constant load conditions were performed. The first test showed a degradation rate of −21.4 μV/h and was operated with H2/30% O2. The second test was performed with the same kind of MEA but different fuel composition (54% H2, 15% CO2 and 31% H2O) and exhibited a reduction of the degradation rate to −5.5 μV/h. The main reason for this lifetime improvement is H2O because its transport from anode to cathode may sweep along PA that soaks catalyst active sites and limits HOR. Moreover, water in rich H2 reformate streams also relieves formation of CO from CO2 via RWGS. The third test was performed with a different kind of MEA (extra PTFE content in GDE) but the same fuel composition than the second one. A higher degradation rate of −22.2 μV/h was observed but it was mainly caused by unprotected shut-downs during operation. Two preliminary long-term tests were also performed with a fuel composition similar to natural gas reformate (54% H2, 14% CO2, 1% CO and 31% H2O). These latest tests revealed that the fuel cell should be operated at higher temperatures to diminish CO catalyst coverage, and that anode purge with dry gases avoids water condensation in gas pipes. In addition, CO poisoning on anode catalyst is time dependent and operation at high current densities enhances CO catalyst coverage.
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long term testing of a high temperature polymer electrolyte membrane fuel cell the effect of reactant gases
Aiche Journal, 2016Co-Authors: Javier F Pinar, Nadine Pilinski, Peter WagnerAbstract:The investigations have been conducted with different oxidants and fuels with the aim of determining the state-of-the-art of commercially available high temperature polymer electrolyte fuel cells based on polybenzimidazole for its application in combined heat and power generation systems. The fuel cell test performed with synthetic reformate (−63 μV/h) showed an increase of anode charge and mass transfer resistances. This behavior has suggested that CO may be generated from the CO2 included in the synthetic reformate via reverse water gas shift reaction. The fuel cell test performed with pure O2 developed the highest degradation rates (−70 μV/h) due to fast oxidative degradation of membrane electrode assembly materials such as cathode catalyst and membrane. Fuel cell operation with H2/air exhibited the lowest degradation rates (−57 μV/h) and it requires longer investigating times to identify the different degradation mechanisms. Moreover, fuel cell tests performed with air suggested longer break-in procedures to complete catalyst activation and redistribution of electrolyte. © 2015 American Institute of Chemical Engineers AIChE J, 2015
Hans Aage Hjuler - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Membrane Electrode Assemblies for High‐Temperature PEM Fuel Cells
Fuel Cells, 2016Co-Authors: María Rau, S.m. Alfaro, Tove Steenberg, André Niedergesäß, Carsten Cremers, Hans Aage HjulerAbstract:This paper will present the characterization of two types of membrane-electrode-assemblies (MEAs) for high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC) working under reformate stream. The important aspects to be considered in the characterization of these MEAs are: (i) presence of contaminants, and (ii) composition of the anode. Start/stop cycling test were performed for two different Dapozol® MEAs using different GDL materials, using first hydrogen and then synthetic reformate as a fuel gas, both with a dew point of 80 °C. With these results the influence of contaminants present in the reformate was compared for the two types of MEAs, showing the superior performance of the Dapozol® 101 MEA under these conditions. The possibility to further enhance the MEAs' resilience against the operation of Reformates by changing the anode catalyst composition was evaluated in a half MEA configuration, considering that the impact of the H2S present in the fuel presents a major issue. For this reason the hydrogen oxidation reaction (HOR) was evaluated for two types of Pt-based electrocatalysts in an anodic half MEA configuration using different hydrogen-rich fuel mixtures. These results provide valuable information for the optimization of the MEA and the anode catalyst for HT-PEMFC.
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Lifetime and degradation of high temperature PEM membrane electrode assemblies
International Journal of Hydrogen Energy, 2015Co-Authors: R. Kerr, S.m. Alfaro, M.t. Romero, C. Terkelsen, Petra Wagner, Maren Rastedt, H. R. Garcia, Tove Steenberg, Hans Aage HjulerAbstract:This work will provide details on some of the high temperature polymer electrolyte membrane (HTPEM) membrane-electrode-assembly (MEA) performance targets most recently achieved by Danish Power Systems. These include (i) MEA performances of >0.67 V at 0.2 A cm−2 using dry H2/Air, (ii) MEA lifetime of 17.000 h at 0.24 A cm−2 using dry H2/Air with an average degradation rate of 9 μV h−1, and (iii) an integrated 5 kW stack/reformer system using methanol reformate as fuel. Post mortem SEM, TEM, micro-tomography and XRD showed membrane thinning and catalyst particle growth that is typical for PEM fuel cells. Platinum particles grew from an initial 2–3 nm to 6–8 nm at the cathode and 4–5 nm at the anode, while the membrane showed thinning from an undoped 40 μm–18 μm in some areas after testing. Studies using reformate have also led to promising initial results, while the rate of degradation for an MEA supplied with wet H2 (30 mol%)/Air for 2000 h was found to be very similar to the rate when supplied with dry H2. In addition to reaching these performance benchmarks, a reduction in the standard deviation for MEA cell voltage at 0.2 A cm−2 to
Maren Rastedt - One of the best experts on this subject based on the ideXlab platform.
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Long-term Operation of High Temperature Polymer Electrolyte Membrane Fuel Cells with Fuel Composition Switching and Oxygen Enrichment†
Fuel Cells, 2018Co-Authors: Francisco Javier Pinar, Alexander Dyck, Maren Rastedt, Peter WagnerAbstract:The performance of commercially available High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) cells was electrochemically (impedance spectroscopy, polarization curves, performance over time) and optically characterized ante and post mortem via micro-computed tomography. Investigations on the performance gain, due to oxygen enrichment of cathode air and the capabilities of the commercial MEAs to switch and operate between pure hydrogen and synthetic dry reformate (78% H2 and 22% CO2), were carried out. Two experiments at constant load conditions were performed, Cycle 1 consisted of 12 h pure hydrogen operation followed by 12 h of synthetic reformate, while Cycle 2 was operated with 1 h of H2 followed by 5 h of synthetic reformate. The results revealed that oxygen enrichment improves mass transport from the gas flow channels to the cathode catalyst layer as well as catalyst utilization. Thus, oxygen concentration increase from 21% (air) to 30% at 0.3 A cm−2 developed a performance improvement of roughly 8%. Only marginally influence on fuel cell performance and degradation was observed in fuel switching experiments. A content of 22% CO2 had little influence on degradation, which could mainly be related to fuel dilution. Besides, micro-computed tomography (µ-CT) investigations revealed similar membrane and catalyst layer degradation for both kinds of fuel switching tests.
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demonstrating feasibility of a high temperature polymer electrolyte membrane fuel cell operation with natural gas reformate composition
International Journal of Hydrogen Energy, 2017Co-Authors: Javier F Pinar, Nadine Pilinski, Maren Rastedt, Peter Wagner, Alexander DyckAbstract:Abstract Experimental data on the performance of a single cell PBI-based HT-PEMFC operated with a fuel composition similar to natural gas reformate and oxygen enriched cathode air are presented. A test studying the effect of CO2, H2O and CO in the fuel on fuel cell performance revealed that the presence of CO2 mainly worsens mass transport, H2O improves proton conduction and CO influences reaction kinetics as well as causing mass transport limitations. A small increase of the O2 concentration in the oxidant provided a boost on performance. Electrical efficiency of the fuel cell was improved from 36.6% with H2/air operation up to 38.2% with synthetic reformate gas/30% O2 enriched air. Three 1000 h long-term tests at constant load conditions were performed. The first test showed a degradation rate of −21.4 μV/h and was operated with H2/30% O2. The second test was performed with the same kind of MEA but different fuel composition (54% H2, 15% CO2 and 31% H2O) and exhibited a reduction of the degradation rate to −5.5 μV/h. The main reason for this lifetime improvement is H2O because its transport from anode to cathode may sweep along PA that soaks catalyst active sites and limits HOR. Moreover, water in rich H2 reformate streams also relieves formation of CO from CO2 via RWGS. The third test was performed with a different kind of MEA (extra PTFE content in GDE) but the same fuel composition than the second one. A higher degradation rate of −22.2 μV/h was observed but it was mainly caused by unprotected shut-downs during operation. Two preliminary long-term tests were also performed with a fuel composition similar to natural gas reformate (54% H2, 14% CO2, 1% CO and 31% H2O). These latest tests revealed that the fuel cell should be operated at higher temperatures to diminish CO catalyst coverage, and that anode purge with dry gases avoids water condensation in gas pipes. In addition, CO poisoning on anode catalyst is time dependent and operation at high current densities enhances CO catalyst coverage.
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Lifetime and degradation of high temperature PEM membrane electrode assemblies
International Journal of Hydrogen Energy, 2015Co-Authors: R. Kerr, S.m. Alfaro, M.t. Romero, C. Terkelsen, Petra Wagner, Maren Rastedt, H. R. Garcia, Tove Steenberg, Hans Aage HjulerAbstract:This work will provide details on some of the high temperature polymer electrolyte membrane (HTPEM) membrane-electrode-assembly (MEA) performance targets most recently achieved by Danish Power Systems. These include (i) MEA performances of >0.67 V at 0.2 A cm−2 using dry H2/Air, (ii) MEA lifetime of 17.000 h at 0.24 A cm−2 using dry H2/Air with an average degradation rate of 9 μV h−1, and (iii) an integrated 5 kW stack/reformer system using methanol reformate as fuel. Post mortem SEM, TEM, micro-tomography and XRD showed membrane thinning and catalyst particle growth that is typical for PEM fuel cells. Platinum particles grew from an initial 2–3 nm to 6–8 nm at the cathode and 4–5 nm at the anode, while the membrane showed thinning from an undoped 40 μm–18 μm in some areas after testing. Studies using reformate have also led to promising initial results, while the rate of degradation for an MEA supplied with wet H2 (30 mol%)/Air for 2000 h was found to be very similar to the rate when supplied with dry H2. In addition to reaching these performance benchmarks, a reduction in the standard deviation for MEA cell voltage at 0.2 A cm−2 to
Chen-yu Chen - One of the best experts on this subject based on the ideXlab platform.
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Experimental characterization of high-temperature proton exchange membrane fuel cells under CO- and methane-containing hydrogen-rich gases
Journal of Applied Electrochemistry, 2018Co-Authors: Chen-yu Chen, Keng-pin HuangAbstract:The objective of this work is to study a high-temperature proton exchange membrane fuel cell using CO- and methane-containing hydrogen-rich gases because of the advantages of high operating temperature and the growing feasibility of using natural gases or methane as the sources of hydrogen-rich reformate gases. According to the experimental results, it is suggested that the fuel cell be operated at 180 °C under reformate gases with high CO concentrations to avoid not only a significant decrease in performance, but also severe potential oscillations. In addition, the anode oxidation reaction is more sensitive to the temperature than the cathode reduction reaction under CO-containing H_2. On the other hand, the effects of methane in the reformate gas on the fuel cell can be ignored because the existence of methane causes neither a decrease in the cell performance nor an increase in the anodic charge transfer resistance. Thus, the CO concentration and operating temperature are still the two dominant parameters with regard to the cell performance under CO- and methane-containing hydrogen-rich gases.Graphical Abstract
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characteristic studies of a pbi h3po4 high temperature membrane pemfc under simulated reformate gases
International Journal of Hydrogen Energy, 2014Co-Authors: Chen-yu Chen, Yi Kuang Chen, Siou Sheng SuAbstract:Abstract A high temperature proton exchange membrane fuel cell is considered a solution to improve the cell performance under CO-contained hydrogen and to simplify the gas purification process of a reformate fuel cell system. In this study, polybenzimidazole-based phosphoric acid-doped fuel cells are studied under simulated reformate gases of different H2, N2 and CO concentrations. The experimental results show that the dilution effect of N2 has a minor impact on the cell performance in absence of CO. However, the CO poisoning increases the charge transfer resistance and leads to a substantial performance drop. This work also reveals that increasing the operating temperature can effectively improve the CO tolerance by suppressing the Pt–CO binding reaction. In addition, the CO poisoning effect becomes more significant in diluted H2. As a result, the CO concentration should be maintained lower than a critical level to prevent a high CO coverage on the catalyst which leads to a noteworthy voltage shut-down, especially in highly diluted H2.
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Effects of Reformate on Proton Exchange Membrane Fuel Cells
2012Co-Authors: Chen-yu Chen, Chun-chi Chen, Ming-pin Lai, Sui-wei Hsu, Wei-hsiang LaiAbstract:A reformate fuel cell system is one of the most promising power generation systems in the future. Thus, it is important to understand the behaviour of a fuel cell in reformate gas. In this study, the fuel cell performance in the simulated reformate gas is studied. From this study, it is concluded that the fuel cell performance is influenced by the operational current, nitrogen concentration and the carbon monoxide concentration for a proton exchange membrane fuel cell which uses Pt/Ru as the anodic catalyst. A voltage fluctuation phenomenon at high carbon monoxide concentrations is observed and discussed in this study.
Joongmyeon Bae - One of the best experts on this subject based on the ideXlab platform.
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A diesel fuel processor for stable operation of solid oxide fuel cells system: II. Integrated diesel fuel processor for the operation of solid oxide fuel cells
International Journal of Hydrogen Energy, 2012Co-Authors: Sangho Yoon, Joongmyeon Bae, Sangho Lee, Thang V. Pham, Sai P. KatikaneniAbstract:Abstract Post-reforming experimental results for the complete removal of light hydrocarbons from diesel reformate are introduced in part I. In part II of the paper, an integrated diesel fuel processor is investigated for the stable operation of SOFCs. Several post-reforming processors have been operated to suppress both sulfur poisoning and carbon deposition on the anode catalyst. The integrated diesel fuel processor is composed of an autothermal reformer, a desulfurizer, and a post-reformer. The autothermal reforming section in the integrated diesel fuel processor effectively decomposes aromatics, and converts fuel into H2-rich syngas. The subsequent desulfurizer removes sulfur-containing compounds present in the diesel reformate. Finally, the post-reformer completely removes the light hydrocarbons, which are carbon precursors, in the diesel reformate. We successfully operate the diesel reformer, desulfurizer, and post-reformer as microreactors for about 2500 h in an integrated mode. The degradation rate of the overall reforming performance is negligible for the 2000 h, and light hydrocarbons and sulfur-containing compounds are completely removed from the diesel reformate.
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Development of a self-sustaining kWe-class integrated diesel fuel processing system for solid oxide fuel cells
International Journal of Hydrogen Energy, 2011Co-Authors: Sangho Yoon, Sangho Lee, Joongmyeon BaeAbstract:Abstract Among high temperature fuel cells, solid oxide fuel cells (SOFCs) possess several advantages such as fuel flexibility, high power density, and high-quality waste heat for cogeneration applications. However, if the Reformates of hydrocarbon fuel are used to operate SOFCs, sulfur poisoning and carbon deposition is observed. Diesel reformate contains sulfur compounds and residual low-molecular-weight (LMW) hydrocarbons, which are formed on the anode of the SOFC. In this study, a new type of diesel fuel processing system was introduced for the stable operation of SOFCs. The novel diesel fuel processor contains three different reaction stages: autothermal reforming (ATR), adsorptive desulfurization, and post-reforming. For the stable operationfof SOFCs, the desulfurization and post-reforming processes are used to eliminate sulfur compounds and residual light hydrocarbons from the diesel reformate. The proposed fuel processor does not require an additional heat exchanger or electrical equipment for the supply of heat or the vaporization of fuel and water. The integrated reactor can be implemented as a self-sustaining reactor due to the exothermic nature of the ATR reaction. The reaction temperature of desulfurization and post-reforming processes are controlled by the arrangement of the reactors and heat exchange through the integrated reactor. The kWe self-sustaining integrated diesel fuel processor was operated for approximately 1000 h, and a reforming efficiency of 60% was achieved. Moreover, the desulfurizer and post-reforming reactor completely removed H2S and light hydrocarbons from the diesel reformate.
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Effects of low hydrocarbons on the solid oxide fuel cell anode
Journal of Solid State Electrochemistry, 2010Co-Authors: Sangho Yoon, Yongmin Kim, Sunyoung Kim, Joongmyeon BaeAbstract:In this work, the effects of ethylene on the solid oxide fuel cell (SOFC) anode were investigated both for an SOFC single cell and an SOFC stack. Two fuels were used to observe the effects that low hydrocarbons (over C1-hydrocarbons) in the reformate gas stream have on the SOFC anode. Methane or ethylene was supplied to the electrolyte-supported SOFC anode. Using ethylene as a fuel, catastrophic degradation of SOFC performance was observed due to ethylene-induced carbon deposition onto the SOFC anode. Thus, a new methodology, termed “post-reforming,” is introduced for the removal of low hydrocarbons (over C1-hydrocarbons) from the reformate gas stream. The CGO-Ru catalyst was selected as the post-reforming catalyst because of its high selectivity for removing low hydrocarbons (over C1-hydrocarbons) and for its long-term stability. The diesel reformer and post-reformer were continuously operated for ∼250 h in coupled-operation mode. The reforming performance was not degraded, and low hydrocarbons (over C1-hydrocarbons) in the diesel reformate were completely removed.