Reaction Characteristics around Triple Phase Boundary in Anode Including Proton Conductor for Solid Oxide Fuel Cell

Abstract

A modified reaction model around a triple phase boundary (TPB) was proposed for solid oxide fuel cells (SOFCs) with an anode containing proton conductor particles to describe the mechanism of anode overpotential reduction. In this model, three kinds of TPBs consisting of nickel metal, oxide ion conductor, proton conductor, and gas phases were considered. It was assumed that the chemical species could be adsorbed within a finite narrow area on each material around the TPB, and the reaction rate in the anode was controlled by the surface reaction between Had and Oad, while all other reactions took place under chemical equilibrium. Based on the reaction model, simple expressions for the anode overpotential could be obtained as functions of the current density related to the oxygen activity. The analytical results agreed with the experimental results in both cases, the conventional anode and new anode incorporating a proton conductor.