Elementary Reaction Models for CO Electrochemical Oxidation on an Ni/YSZ Patterned Anode

Abstract

Analysis of recent experimental impedance spectra and polarization curves of nickel/yttria-stabilized zirconia (Ni/YSZ) patterned anode of a solid oxide fuel cell (SOFC) are used to determine the limiting steps in CO electrochemical oxidation kinetics. A comprehensive 1D model is proposed for the prediction of the steady-state polarization curve of a patterned anode SOFC. The model incorporates gas species adsorption/desorption with surface diffusion and one of two possible charge transfer reaction steps: O charge transfer reaction [O2−(YSZ)+(Ni)+↔(YSZ)+O(Ni)+2e−], or CO charge transfer reaction [O2−(YSZ)+CO(Ni)↔(YSZ)+CO2(Ni)+2e−]. We show that the mechanism incorporating charge transfer between adsorbed CO and oxygen vacancy is able to better predict the experimental data. We estimate some of the model parameters, such as the exchange current density and charge transfer coefficient by fitting the simulation of the polarization curves to the experimental data.