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Effect of electrode Pt-loading and cathode flow-field plate type on the degradation of PEMFC

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Journal of Energy Chemistry 2019年第8期28卷 95-103,I0005页

作者： Lijuan Qu Zhiqiang Wang Xiaoqian Guo Wei Song Feng Xie Liang He Zhigang Shao Baolian Yi fuel cell system and engineering group Dalian Institute of Chemical Physics Chinese Academy of SciencesDalian 116023 Liaoning China University of Chinese Academy of Sciences Beijing 100049 China

The electrode Pt-loading has an effect on the number of active sites and the thickness of catalyst layer,which has huge influence on the mass transfer and water management during dynamic process in PEMFCs. In this study, membrane electrode assemblies with different Pt-loadings were prepared, and PEMFCs were assembled using those membrane electrode assemblies with traditional solid plate and water transport plate as cathode flow-field plates, respectively. The performance and electrochemical surface area of cells were characterized to evaluate the membrane electrode assemblies degradation after rapid currentvariation cycles. Scanning electron microscope and transmission electron microscope were used to investigate the decay of catalyst layers and Pt/C catalyst. With the increase of Pt-loading, the performance degradation of membrane electrode assemblies will be mitigated. But higher Pt-loading means thicker catalyst layer, which leads to a longer pathway of mass transfer, and it may result in carbon material corrosion in membrane electrode assemblies. The decay of Pt/C catalyst in cathode is mainly caused by the corrosion of carbon support, and the degradation of anode Pt/C catalyst is a consequence of migration and aggregation of Pt particles. And using water transport plate is beneficial to alleviating the age of cathode Pt/C catalyst.

关键词： Proton exchange membrane fuel cell Electrode platinum loading Current-variation cycle Traditional solid plate Water transport plate

Research progress of Pt and Pt-based cathode electrocatalysts for proton-exchange membrane fuel cells

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Chinese Physics B 2022年第12期31卷 619-628页

作者： Ni Suo Longsheng Cao Xiaoping Qin Zhigang Shao fuel-cell system and engineering Laboratory Key Laboratory of Fuel Cells&Hybrid Power SourcesDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023China

Proton-exchange membrane fuel cells(PEMFCs)have been widely used commercially to solve the energy crisis and environmental *** oxygen reduction reaction(ORR)at the cathode is the rate-determining step in ***(Pt)catalysts are used to accelerate the ORR ***’s scarcity,high cost,and instability in an acidic environment at high potentials seriously hinder the commercialization of ***,studies should explore electrocatalysts with high catalytic activity,enhanced stability,and low-Pt *** review briefly introduces the research progress on Pt and Pt-based ORR electrocatalysts for PEMFCs,including anticorrosion catalyst supports,Pt,and Pt-based alloy *** preparation technology and material characterization of Pt-based ORR electrocatalysts are necessary to improve the performance and corresponding reaction mechanisms.

关键词： electrocatalysts oxygen reduction reaction activity stability

Modeling development on the meso-scale reacting transport phenomena in proton exchange membrane fuel cells

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Acta Mechanica Sinica 2013年第3期29卷 370-378页

作者： Jianliang Yuan Yu Xiao Department of Energy Sciences Lund University fuel cell system and engineering Laboratory Dalian Institute of Chemical Physics Chinese Academy of Science

The catalyst layer （CL） of proton exchange mem-brane fuel cell （PEMFC） involves various particles and pores in meso-scale, which has an important effect on the mass, charge （proton and electron） and heat transport coupled with the electrochemical reactions. The coarse-grained molecular dynamics （CG-MD） method is employed as a meso-scale structure reconstruction technique to mimic the self-organization phenomena in the fabrication steps of a CL. The meso-scale structure obtained at the equilibrium state is further analyzed by molecular dynamic （MD） software to provide the necessary microscopic parameters for understanding of multi-scale and-physics processes in CLs. The primary pore size distribution （PSD） and active platinum （Pt） surface areas are also calculated and then compared with the experiments. In addition, we also highlight the implementation method to combine microscopic elementary kinetic reaction schemes with the CG-MD approaches to provide insight into the reactions in CLs. The concepts from CG modeling with particle hydrodynamics （SPH） and the problems on coupling of SPH with finite element modeling （FEM） methods are further outlined and discussed to understand the effects of the meso-scale transport phenomena in fuel cells.

关键词： CG-MD · Meso-scale · Reaction · Catalyst layer · fuel cell

A novel graphite/phenolic resin bipolar plate modified by doping carbon fibers for the application of proton exchange membrane fuel cells

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Progress in Natural Science:Materials International 2020年第6期30卷 876-881页

作者： Bo Lv Zhigang Shao Liang He Yong Gou Shucheng Sun fuel cell system and engineering Laboratory Key Laboratory of Fuel Cells & Hybrid Power Sources Dalian Institute of Chemical Physics Chinese Academy of Sciences University of Chinese Academy of Sciences

In this study, the carbon fibers treated by three methods were selected as a reinforcement to investigate the influence on the properties of composite bipolar plates. The properties and microstructure of the composite bipolar plate were characterized by the four-point probe, universal test machine, contact angle tester and scanning electron microscopy. The optimum treatment methods and the fiber content were analysed. The results showed that the carbon fibers treated by Fenton reagent for 2 h exhibited the best performance, which could improve the electrical conductivity and the flexural strength for composite bipolar plate. Besides, the optimal content content of carbon fibers treated by Fenton reagent was 4%. The maximum power density of the PEMFC with the composite bipolar plates could reach 662.75 m W cmin H-air conditions. Therefore, the phenolic resin/graphite composite bipolar plate modified by doping carbon fibers was a promising candidate for bipolar plate materials for PEMFC.

关键词： PEM fuel cell Natural graphite Phenolic resin Composite bipolar plate

Experimental investigation on degradation mechanism of membrane electrode assembly at different humidity under automotive protocol

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Chinese Journal of Chemical engineering 2023年第4期56卷 70-79页

作者： Jiajun Wang Wenbin Yang Jiangtao Geng Zhigang Shao Wei Song fuel cell system and engineering Laboratory Key Laboratory of Fuel Cells and Hybrid Power SourcesDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023China University of Chinese Academy of Sciences Beijing 100039China

Humidity can affect the attenuation of MEA(membrane electrode assembly), however, the relationship between humidity and MEA decays is complex and ambiguous in realistic application. Herein, we design a simulating automotive protocol, performed on five single fuel cells under RH(relative humidity) 100%,RH 80%, RH 64%, and RH 40%, RH 10%, respectively, to study the relationship of MEA decays and humidity and suggest optimized humidity range to extend the durability. With the electrochemical impedance spectroscopy, cyclic voltammetry, X-ray fluorescence, X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, the four degradation mechanisms about catalyst layer, including Pt dissolution, Pt coarsening, carbon corrosion and ionomer degradation, are observed. Pt coarsening and carbon corrosion are accelerated by higher water content at high humidity. Ionomer degradation and Pt dissolution are enhanced in low humidity. With the linear sweep voltammetry, ion chromatography,nuclear magnetic resonance, tensile test and scan electron microscope, chemical and mechanical degradation in proton exchange membrane are all observed in these five fuels. Chemical degradation, characterized by membrane thinning and more fluoride loss, occurred markedly in RH 10%. Mechanical degradation, characterized by the non-uniformity thickness and bad mechanical properties, is more pronounced in RH 100%, RH 80%, RH 64%. These two degradations are in a moderate level in RH 40%. The research suggests that the RH range from 64% to 40% is conductive to mitigate the degradation of MEAs operated in automotive applications.

关键词： fuel cell Simulating automotive protocol Relative humidity Degradation Membrane

Ti/(Ti,Cr)N/CrN multilayer coated 316L stainless steel by arc ion plating as bipolar plates for proton exchange membrane fuel cells

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Journal of Energy Chemistry 2017年第1期26卷 168-174页

作者： Shengli Wang Ming Hou Qing Zhao Yongyi Jiang Zhen Wang Huizhe Li Yu Fu Zhigang Shao fuel cell system and engineering Laboratory Dalian Institute of Chemical Physics Chinese Academy of Sciences University of Chinese Academy of Sciences Dalian Sunrise Power Co. LTD

Arc ion plating (AIP) is applied to form Ti/(Ti,Cr)N/CrN multilayer coating on the surface of 316L stainless steel (SS316L) as bipolar plates for proton exchange membrane fuel cells (PEMFCs). The characterizations of the coating are analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Interfacial contact resistance (ICR) between the coated sample and carbon paper is 4.9 m Omega cm(2) under 150 N/cm(2), which is much lower than that of the SS316L substrate. Potentiodynamic and potentiostatic tests are performed in the simulated PEMFC working conditions to investigate the corrosion behaviors of the coated sample. Superior anticorrosion performance is observed for the coated sample, whose corrosion current density is 0.12 mu A/cm(2). Surface morphology results after corrosion tests indicate that the substrate is well protected by the multilayer coating. Performances of the single cell with the multilayer coated SS316L bipolar plate are improved significantly compared with that of the cell with the uncoated SS316L bipolar plate, presenting a great potential for PEMFC application. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

关键词： Stainless steel bipolar plate Proton exchange membrane fuel cell Arc ion plating Multilayer coating

Enhanced electrocatalytic performance of ultrathin PtNi alloy nanowires for oxygen reduction reaction

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Frontiers in Energy 2017年第3期11卷 260-267页

作者： Hongjie ZHANG Yachao ZENG Longsheng CAO Limeng YANG Dahui FANG Baolian YI Zhigang SHAO fuel cell system and engineering Laboratory Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 China University of the Chinese Academy of Sciences Beijing 100039 China

In this paper, ultrathin Pt nanowires （Pt NWs） and PtNi alloy nanowires （PtNi NWs） supported on carbon were synthesized as electrocatalysts for oxygen reduction reaction （ORR）. Pt and PtNi NWs catalysts composed of interconnected nanoparticles were prepared by using a soft template method with CTAB as the surface active agent. The physical characterization and electrocatalytic perfor- mance of Pt NWs and PtNi NWs catalysts for ORR were investigated and the results were compared with the commercial Pt/C catalyst. The atomic ratio of Pt and Ni in PtNi alloy was approximately 3 to 1. The results show that after alloying with Ni, the binding energy of Pt shifts to higher values, indicating the change of its electronic structure, and that Pt3Ni NWs catalyst has a significantly higher electrocatalytic activity and good stability for ORR as compared to Pt NWs and even Pt/C catalyst. The enhanced electrocatalytic activity of Pt3Ni NWs catalyst is mainly resulted from the downshifted-band center of Pt caused by the interaction between Pt and Ni in the alloy, which facilitates the desorption of oxygen containing species （Oads or OHads） and the release of active sites.

关键词： PtNi alloy nanowires oxygen reduction reaction enhanced activity good stability

New insight into effect of potential on degradation of Fe-N-C catalyst for ORR

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Frontiers in Energy 2021年第2期15卷 421-430页

作者： Yanyan GAO Ming HOU Manman QI Liang HE Haiping CHEN Wenzhe LUO Zhigang SHAO fuel cell system and engineering Laboratory Key Laboratory of Fuel Cells&Hybrid Power SourcesDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023China University of Chinese Academy of Sciences Beijing 100049China

In recent years,Fe-N-C catalyst is particularly attractive due to its high oxygen reduction reaction(ORR)activity and low cost for proton exchange membrane fuel cells(PEMFCs).However,the durability problems still pose challenge to the application of Fe-N-C *** considerable work has been done to investigate the degradation mechanisms of Fe-N-C catalyst,most of them are simply focused on the active-site decay,the carbon oxidation,and the demetalation *** fact,the 2e−pathway in the ORR process of Fe-N-C catalyst would result in the formation of H2O2,which is proved to be a key degradation *** this paper,a new insight into the effect of potential on degradation of Fe-N-C catalyst was provided by quantifying the H2O2 *** this case,stability tests were conducted by the potential-static method in O2 saturated 0.1 mol/L *** the tests,H2O2 was quantified by rotating ring disk electrode(RRDE).The results show that compared with the loading voltage of 0.4 V,0.8 V,and 1.0 V,the catalysts being kept at 0.6 V exhibit a highest H2O2 *** is found that it is the combined effect of electrochemical oxidation and chemical oxidation(by aggressive radicals like H2O2/radicals)that triggered the highest H2O2 release rate,with the latter as the major cause.

关键词： proton exchange membrane fuel cells(PEMFCs) oxygen reduction reaction(ORR) Fe-N-C catalyst potential H2O2 degradation

Microstructure formation mechanism of catalyst layer and its effect on fuel cell performance:Effect of dispersion medium composition

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Journal of Energy Chemistry 2022年第10期31卷 588-598,I0015页

作者： Hong Ren Xiangchao Meng Yongli Lin Zhigang Shao fuel cell system and engineering Laboratory Key Laboratory of Fuel Cells&Hybrid Power SourcesDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina University of Chinese Academy of Sciences Beijing 100049China

The design of the catalyst layer(CL)offers a feasible way to realize the commercialization of proton exchange membrane fuel cells(PEMFCs).An in-depth understanding of catalyst inks is critical to achieving the optimal CL structure and cell *** this work,the effects of the solvent evaporation process during ink drying on the formation of the CL microstructure are particularly considered to reveal the structure-property correlations among the catalyst ink,drying process,CL microstructure and fuel cell *** increase in the alcohol content of the catalyst ink increases the amount of free ionomers while allowing the ionomer backbone to be more stretched in the dispersion *** higher alcohol content contributes to rapid solvent evaporation and thus inhibits the formation of coffee rings;as a result,a more developed ionomer network with a denser pore structure is ***,the alcohol-rich electrode exhibits better proton conduction capability,but higher oxygen transport *** complex fuel cell operating conditions,a catalyst ink formulation with 50 wt%alcohol content is preferred due to its proper ionomer and pore size distribution,providing satisfactory fuel cell performance.

关键词： Proton exchange membrane fuel cell Ink composition Ionomer distribution Pore structure Ink drying process