CURRENT DISTRIBUTION AT POROUS ELECTRODE-SOLID OXIDE ELECTROLYTE INTERFACE

A two-dimensional model is developed fur transport of oxygen in a poro us solid oxide fuel cell (SOFC) cathode with negligible oxygen ion con ductivity in the bulk. Adsorption and surface diffusion of oxygen adso rbates on the pore walls, interfacial diffusion of adsorbates, and ele ctrochemical reaction kinetics at the electrode/electrolyte interface are considered, as well as the nonuniform current and potential distri bution in the electrolyte. In particular; the effect of a nonuniform c urrent distribution along the electrode/electrolyte interface is inves tigated. The results are compared to a previously developed one-dimens ional model for SOFC perovskite cathodes based on the porous electrode theory. The two models agree well, except in the case of strong inter facial mass-transfer limitations. The benefit of an expanded reaction zone along the electrode/electrolyte interface is demonstrated. Howeve r, nonuniform current distribution at high current levels caused by di ffusion limitations at the interface reduces the effective size of the reaction zone and restricts this zone close to the three-phase bounda ry.