Authors: Saiful Hasmady Kazuyoshi Fushinobu
Publish Date: 2014/07/12
Volume: 18, Issue: 12, Pages: 3387-3405
Abstract
This paper reports the development of mathematical model that bridges PEMFC transport phenomena with surface reaction kinetics in rough and heterogeneous electrodes in which specifically the anode is modeled under carbon monoxide contamination The mathematical bridging is done by converting surface concentration of reactants and contaminant into surface coverage of relevant adsorbates using the LangmuirFreundlich isotherm to statistically include heterogeneity in binding site energetics Thermodynamically optimized kinetic rate and equilibrium constants are calculated using coveragedependent activation energies and provided as input to the HOR ORR and a kineticbased limiting current model developed to solve for the distribution of activation overpotential A novel model for a closedform calculation of activation overpotential is proposed to allow numerical investigation via a galvanostatic approach The kinetic reaction models are highly coupled with threedimensional transport equations and solved iteratively under singlephase and steadystate 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 operating temperatures in which good agreement is found The results confirm that a LangmuirFreundlich isotherm could be a more suitable isotherm compared to the extensively used Langmuirspecific isotherm for rough heterogeneous surfaces physically found in PEMFC catalysts Results from the model show that rate of HOR is higher under the ribs of the cell since most of the active sites under channel are blocked with CO with the effect exacerbated at lower temperatures
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