• Bergmann, Alexander
• Kovtunenko, Victor
• Schatt, Eduard-Emilian
• Karpenko-Jereb, Larisa
• Verebes, Pal

Abstract

The work is devoted to development of a kinetic model describing the chemical degradation of the perfluorinated ionomer in the catalyst layers as well as in the membrane during the operation in a polymer electrolyte fuel cell. <br/><br/>The suggested model is based on the following approximations: a) hydrogen peroxide (H2O2) formation proceeds in both catalyst layers via the two-electron oxygen reduction (1); b) an amount of the hydrogen peroxide is reduced into water according to the reaction (2); c) the peroxide is transported via diffusion in the membrane, micro-porous and macro-porous layers; d) in ionomer, the peroxide reacts with metal cations via the Fenton reaction and (3) builds hydroxyl radicals; e) the hydroxyl radicals split the side chains of the ionomer, which contain the functional groups; f) the boundary conditions are identically to the conditions defined in [1]. <br/> <br/>(1) O2 + 2H+ + 2e-  H2O2E2eORR = 0.695 V2e oxygen reduction <br/>(2) H2O2 + 2H+ + 2e-  2H2OEH2O2d = 1.760 VH2O2 reduction<br/>(3) Fe2+ + H2O2 + H+  Fe3+ + OH. + H2OFenton reaction<br/><br/>The model has been applied to analyze the effects of operating parameters such as pressure, temperature and relative humidity on the degradation of the perfluorinated ionomer in the operating fuel cell.The model enables to monitor time-dependent changes in the ionic conductivity of the membrane, the thickness of the membrane and the catalyst layer, acid group concentration of the ionomer as well as the amount of HF and CO2 released. <br/><br/>Acknowledgment. The work has been financially supported by the Austrian Research Promotion Agency (FFG), the Austrian Ministry for Transport, Innovation and Technology (BMVIT) and the company AVL List GmbH: Program “Mobilität der Zukunft”, Project “FC-DIAMOND” (No. 850328, 2015-2018) - PEM Fuel Cell DegradatIon Analysis and MinimizatiON MethoDology Based on Joint Experimental and Simulation Techniques. <br/><br/>[1] Wong K, Kjeang E. Macroscopic in-situ modeling of chemical membrane degradation in polymer electrolyte fuel cells // Journal of the Electrochemical Society 2014, 161 (9): F823-F832. <br/>

Topics

• porous
• impedance spectroscopy
• polymer
• simulation
• Oxygen
• Hydrogen