The Experts below are selected from a list of 21432 Experts worldwide ranked by ideXlab platform
Hongtan Liu - One of the best experts on this subject based on the ideXlab platform.
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Effects of carbon corrosion on Mass Transfer Losses in proton exchange membrane fuel cells
International Journal of Hydrogen Energy, 2017Co-Authors: Xu Zhang, Yupeng Yang, Liejin Guo, Hongtan LiuAbstract:Abstract Carbon corrosion in proton exchange membrane fuel cells (PEMFC) causes not only kinetic degradation, but also damages to electrode microstructure and hydrophobicity, which can lead to increases in Mass transport resistance. While much attention has been paid to catalyst degradation and kinetic Losses, the increases in Mass Transfer Loss is also a very serious problem and thus it is the focus of this work. To induce carbon corrosion, accelerated stress test (AST) by holding the cell potential at 1.4 V is used. The AST procedure is interrupted periodically to record cell performance after each period of AST at three different current densities. Experiment results show that at low current density, the decrease in cell voltage is linear with time of AST, but the rate in cell voltage decrease accelerates after some period of AST at medium and high current densities. It is hypothesized that such an accelerated voltage decrease is from the increase in Mass Transfer Loss due to water flooding in the MEA. Further experiments with either reduced inlet air humidification or reduce air flow rate confirm that water flooding in the MEA is the cause for the sharp decline in cell voltages. A phenomenon that the cell voltage increases, or the rate in cell voltage reduction decreases as cell degradation progresses is repeatedly observed. It is determined that such a phenomenon is mainly caused by the enhanced phase-change-induced flow (PCI) due to the higher heat generation rate in a more severely degraded cell. The experimental results also provide some insights on how to optimize operating conditions for degraded fuel cells.
Minggao Ouyang - One of the best experts on this subject based on the ideXlab platform.
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Gradient design of Pt/C ratio and Nafion content in cathode catalyst layer of PEMFCs
International Journal of Hydrogen Energy, 2017Co-Authors: Guang-ying Chen, Cheng Wang, Yi-jie Lei, Jianbo Zhang, Zhi-ming Mao, Zongqiang Mao, Jian-wei Guo, Minggao OuyangAbstract:Abstract In order to increase the utilization of Pt, reduce Mass Transfer Loss and improve the performance of polymer electrolyte membrane fuel cells (PEMFCs) under low humidity and high current densities, the cathode catalyst layers with two layers of different Pt/C ratio and Nafion content are fabricated and evaluated. Polarization curves (IVs), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are employed to characterize and compare the effects of Pt/C ratio and Nafion content gradient on the performance of PEMFCs under different humidification conditions. The results indicate that the performance of the membrane electrode assembly (MEA) can be significantly improved via allocating more Nafion and Pt/C in the sublayer near the membrane in cathode catalyst layer. The MEA with optimal gradient cathode catalyst layer results in improved catalysts utilization compared to MEA with single cathode catalyst layer, 0.403 g kW rated −1 and 0.711 g kW rated −1 under 80 RH% and 20 RH%, respectively. The areal power density of the optimal MEA is 28.4% and 135.7% higher than the conventional single-layer catalyst layer MEA under high and low humidity, respectively.
Xu Zhang - One of the best experts on this subject based on the ideXlab platform.
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Effects of carbon corrosion on Mass Transfer Losses in proton exchange membrane fuel cells
International Journal of Hydrogen Energy, 2017Co-Authors: Xu Zhang, Yupeng Yang, Liejin Guo, Hongtan LiuAbstract:Abstract Carbon corrosion in proton exchange membrane fuel cells (PEMFC) causes not only kinetic degradation, but also damages to electrode microstructure and hydrophobicity, which can lead to increases in Mass transport resistance. While much attention has been paid to catalyst degradation and kinetic Losses, the increases in Mass Transfer Loss is also a very serious problem and thus it is the focus of this work. To induce carbon corrosion, accelerated stress test (AST) by holding the cell potential at 1.4 V is used. The AST procedure is interrupted periodically to record cell performance after each period of AST at three different current densities. Experiment results show that at low current density, the decrease in cell voltage is linear with time of AST, but the rate in cell voltage decrease accelerates after some period of AST at medium and high current densities. It is hypothesized that such an accelerated voltage decrease is from the increase in Mass Transfer Loss due to water flooding in the MEA. Further experiments with either reduced inlet air humidification or reduce air flow rate confirm that water flooding in the MEA is the cause for the sharp decline in cell voltages. A phenomenon that the cell voltage increases, or the rate in cell voltage reduction decreases as cell degradation progresses is repeatedly observed. It is determined that such a phenomenon is mainly caused by the enhanced phase-change-induced flow (PCI) due to the higher heat generation rate in a more severely degraded cell. The experimental results also provide some insights on how to optimize operating conditions for degraded fuel cells.
Jhao-ruei Ciou - One of the best experts on this subject based on the ideXlab platform.
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Effects of surface chemical states of carbon nanotubes supported Pt nanoparticles on performance of proton exchange membrane fuel cells
International Journal of Hydrogen Energy, 2011Co-Authors: Yu-chun Chiang, Jhao-ruei CiouAbstract:Abstract This study synthesized platinum (Pt) nanoparticles supported on carbon nanotubes (CNTs) using a microwave-assisted polyol method. The oxidation treatment of CNTs introduced primarily –OH and –COOH groups to the CNTs, thereby enhancing the reduction of Pt ionic species, resulting in smaller Pt particles with improved dispersion and attachment properties. The Pt particles supported on oxidized CNTs displayed superior durability to those on pristine CNTs or commercially available Pt/C. These improvements are most likely associated with the percentage of metallic Pt in the particles. After 400 cycles, the Losses of electrochemical surface area in Pt nanoparticle supported on oxidized CNTs and pristine CNTs catalysts were 66 and 84%, respectively, of that associated with commercial Pt/C. A single proton exchange membrane fuel cell using Pt supported on oxidized CNTs at the cathode with a total catalytic loading of 0.6 Pt mg cm −2 exhibited the highest power density of 890 mW cm −2 and displayed a lower Mass Transfer Loss, compared to Pt/C.
Guang-ying Chen - One of the best experts on this subject based on the ideXlab platform.
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Gradient design of Pt/C ratio and Nafion content in cathode catalyst layer of PEMFCs
International Journal of Hydrogen Energy, 2017Co-Authors: Guang-ying Chen, Cheng Wang, Yi-jie Lei, Jianbo Zhang, Zhi-ming Mao, Zongqiang Mao, Jian-wei Guo, Minggao OuyangAbstract:Abstract In order to increase the utilization of Pt, reduce Mass Transfer Loss and improve the performance of polymer electrolyte membrane fuel cells (PEMFCs) under low humidity and high current densities, the cathode catalyst layers with two layers of different Pt/C ratio and Nafion content are fabricated and evaluated. Polarization curves (IVs), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are employed to characterize and compare the effects of Pt/C ratio and Nafion content gradient on the performance of PEMFCs under different humidification conditions. The results indicate that the performance of the membrane electrode assembly (MEA) can be significantly improved via allocating more Nafion and Pt/C in the sublayer near the membrane in cathode catalyst layer. The MEA with optimal gradient cathode catalyst layer results in improved catalysts utilization compared to MEA with single cathode catalyst layer, 0.403 g kW rated −1 and 0.711 g kW rated −1 under 80 RH% and 20 RH%, respectively. The areal power density of the optimal MEA is 28.4% and 135.7% higher than the conventional single-layer catalyst layer MEA under high and low humidity, respectively.