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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

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 performance.In 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 performance.An 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 medium.The 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 obtained.Therefore,the alcohol-rich electrode exhibits better proton conduction capability,but higher oxygen transport resistance.For 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

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

One New Zinc Coordination Polymer Based on 2-Chloro-benzoate and 4,4'-Bipyridine: Synthesis, Crystal Structure and Luminescence

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Chinese Journal of Structural Chemistry 2013年第8期32卷 1229-1235页

作者：马德运郭海福覃亮 School of Chemistry and Chemical engineering Zhaoqing University Key Laboratory of fuel cell Technology of Guangdong Province South China University of Technology

A Zn-based coordination polymer [Zn（2-cb）2（4,4′-bpy）0.5]n （1, 2-cb = 2-chloro- benzoate, 4,4＇-bpy = 4,4′-bipyridine） was prepared by hydrothermal synthesis using 2-chloro- benzoic acid and 4,4′-bipyridyl as ligands. The compound was characterized by elemental analysis, IR, TGA, and X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group PI with a = 8.0471（5）, b = 9.7338（6）, c = 11.7830（7） A, a = 96.2230（10）, β = 92.542（2）, γ = 103.7560（10）°, V = 888.84（9） A3, Z = 2, Mr = 454.57, Dc = 1.698 g/cm3,μ（MoKa） = 1.708 mm.1, F（000） = 458, the final R = 0.0359 and wR = 0.0936 for 3167 observed reflections with I 〉 2σ（I）. The crystal analysis indicates that 1 exhibits a 1-D chain structure constructed by 4,4′-bpy and a dicaryon secondary-building-unit of [Zn2（2-cb）4]. Luminescence analysis revealed that compound 1 emits blue fluorescence with a fluorescence lifetime of 55.03 ns.

关键词： Zn-based coordination polymer hydrothermalsynthesis crystal structure luminescence

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：索妮曹龙生秦晓平邵志刚 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 pollution.The oxygen reduction reaction(ORR)at the cathode is the rate-determining step in PEMFCs.Platinum(Pt)catalysts are used to accelerate the ORR kinetics.Pt’s scarcity,high cost,and instability in an acidic environment at high potentials seriously hinder the commercialization of PEMFCs.Therefore,studies should explore electrocatalysts with high catalytic activity,enhanced stability,and low-Pt loading.This review briefly introduces the research progress on Pt and Pt-based ORR electrocatalysts for PEMFCs,including anticorrosion catalyst supports,Pt,and Pt-based alloy electrocatalysts.Advanced 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

Preparation and characterization of Ti_(0.7)Sn_(0.3)O_2 as catalyst support for oxygen reduction reaction

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Journal of Energy Chemistry 2014年第3期23卷 331-337页

作者： Yuan Gao Ming Hou Zhigang Shao Changkun Zhang Xiaoping Qin Baolian Yi fuel cell system and engineering Laboratory Dalian Institute of Chemical PhysicsChinese Academy of Sciences Graduate School of Chinese Academy of Sciences

Sn-doped TiO2 nanoparticles with high surface area of 125.7 m2·g-1 are synthesized via a simple one-step hydrothermai method and explored as the cathode catalyst support for proton exchange membrane fuel cells.The synthesized support materials are studied by X-ray diffraction analysis,energy dispersive X-ray spectroscopy and transmission electron microscopy.It is found that the conductivity has been greatly improved by the addition of 30 mol%Sn and Pt nanoparticles are well dispersed on Ti0.7Sn0.3O2 support with an average size of 2.44 run.Electrochemical studies show that the Ti0.7Sn0.3O2 nanoparticles have excellent electrochemical stability under a high potential compared to Vulcan XC-72.The as-synthesized Pt/Ti0.7Sn0.3O2 exhibits high and stable electrocatalytic activity for the oxygen reduction reaction.The Pt/Ti0.7Sn0.3O2 catalyst reserves most of its electrochemically active surface area（ECA）,and its half wave potential difference is 11 mV,which is lower than that of Pt/XC-72（36 mV） under 10 h potential hold at 1.4 V vs.NHE.In addition,the ECA degradation of Pt/Ti0.7Sn0.3O2is 1.9 times lower than commercial Pt/XC-72 under 500 potential cycles between 0.6 V and 1.2 V vs.NHE.Therefore,the as synthesized Pt/Ti0.7Sn0.3O2 can be considered as a promising alternative cathode,catalyst for proton exchange membrane fuel cells.

关键词： tin titanium oxide support durability proton exchange membrane fuel cells

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

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

Ti_(4)O_(7) supported IrO_(x) for anode reversal tolerance in proton exchange membrane fuel cell

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Frontiers in Energy 2022年第5期16卷 852-861页

作者： Yonghuan LI Wei SONG Guang JIANG Yue YANG Hongmei YU Zhigang SHAO Fangwei DUAN Yingxuan YANG 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 the Chinese Academy of Sciences Beijing 100039China State Grid Liaoning Electric Power Research Institute Shenyang 110055China

fuel starvation can occur and cause damage to the cell when proton exchange membrane fuel cells operate under complex working conditions.In this case,carbon corrosion occurs.Oxygen evolution reaction(OER)catalysts can alleviate carbon corrosion by introducing water electrolysis at a lower potential at the anode in fuel shortage.The mixture of hydrogen oxidation reaction(HOR)and unsupported OER catalyst not only reduces the electrolysis efficiency,but also influences the initial performance of the fuel cell.Herein,Ti_(4)O_(7) supported IrO_(x) is synthesized by utilizing the surfactant-assistant method and serves as reversal tolerant components in the anode.When the cell reverse time is less than 100 min,the cell voltage of the MEA added with IrO_(x)/Ti_(4)O_(7) has almost no attenuation.Besides,the MEA has a longer reversal time(530 min)than IrO_(x)(75 min),showing an excellent reversal tolerance.The results of electron microscopy spectroscopy show that IrO_(x) particles have a good dispersity on the surface of Ti_(4)O_(7) and IrO_(x)/Ti_(4)O_(7) particles are uniformly dispersed on the anode catalytic layer.After the stability test,the Ti_(4)O_(7) support has little decay,demonstrating a high electrochemical stability.IrO_(x)/Ti_(4)O_(7) with a high dispersity has a great potential to the application on the reversal tolerance anode of the fuel cell.

关键词： proton exchange membrane fuel cell(PEMFC) fuel starvation cell reverse reversal tolerance anode oxygen evolution reaction