Gas Conversion Impedance: SOFC Anodes in H2/H2O Atmospheres

Abstract

Impedance spectra are obtained in H-2/H2O on Ni/YSZ cermet anodes. These impedance spectra are fitted to the equivalent circuit LR(RQ)(1)(RQ)(2)(RC)(3) The subcircuit (RC)(3) is found to have a capacitance in the order of 0.1-1.1F only when the current-bearing electrodes are in separate atmospheres. This impedance is derived analytically and shown to represent the change in composition of a gas volume above the anode. This impedance has no direct relations to anode composition or electrochemical performance, but will inevitably contribute to the measured polarisation resistance.