Thermal and water management is a critical issue in PEFCs. In this research, the thermal behavior of PEFC is focused. The objective is to understand the influence of heat on cell performance both by experiment and theoretical analysis, as well as improving cell performance and reliability. In order to investigate the theoretical behavior, especially in the catalyst layer where the electrochemical reactions occur, a detailed modeling of heterogeneous surface reaction coupled with reactant transport is needed. In this paper, a theoretical model that improves the dependency of the exchange current density with reactant concentrations by applying data from a known surface reaction steps found in catalysis is developed. It served as a preliminary step before the thermal-electrochemical behavior of a PEFC can be fully understood.
This paper reports a numerical study on the effects of CO contamination towards the distribution of chemical species, surface coverage, current density and temperature inside a PEMFC using a kinetics-transport bridging model. Bridging is done by linking macro-scale, macro-homogeneous transport phenomena models with micro-scale contamination kinetics model via conversion of the surface concentration of the reactants on the rough electrocatalyst into surface site coverage of the participating adsorbates using Langmuir-Freundlich isotherm. The effects of CO contamination is investigated by solving the bridged model iteratively under steady state, single phase and non-isothermal conditions in three-dimensions. The effect of CO-ad presence on the electrocatalyst surface towards distribution of chemical species, current density and temperature is discussed at cell temperature of 70°C and two nominal current densities of 0.5 and 1.0 A/cm 2 . The results show that the region under the ribs at anode catalyst layer registered higher magnitude of current density due to blockage from CO-ad under channel. The anode catalyst layer also shows an increase in local temperature comparable to the cathode catalyst layer that can aggravate dehydration of the membrane, which in turn affect its durability in long-term operation.
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