Inclusion of non-isothermal effects in modeling electrochemical kinetics of contaminated pem fuel cell electrodes

Abstract

This paper reports the development of a thermodynamically optimized theoretical bridging model for a PEMFC anode and cathode reaction heterogeneous kinetics, in which specifically the anode is modeled under carbon monoxide contamination. Bridging is done by converting the numerically solved surface concentration of reactants and contaminant into their respective surface coverage using the Langmuir-Freundlich isotherm. Thermodynamically optimized kinetic rate constants are calculated using coverage-dependent activation energies and provided as input to an electrode reaction rate model developed to obtain the overpotential. The kinetic reaction model is then coupled again with three-dimensional transport equations and solved iteratively under steady state and non-isothermal conditions. Comparison is done with respect to two sets of available literature data in order to test the kinetic model validity under variation of CO concentrations and cell temperatures, in which good agreement is found. The results confirm that a Langmuir-Freundlich isotherm could be a more suitable isotherm compared to the extensively used Langmuir-only isotherm for rough heterogeneous surfaces physically found in PEMFC catalysts. The effects of temperature distribution towards contamination behavior in the cell are further explored.