Improving the Catalytic Activity of (Ba_0.95La_0.05)(Fe_0.8Zn_0.2)O_3−δ Protonic Ceramic Fuel Cell Cathodes by Cation Substitution

Abstract

(Ba0.95La0.05)(Fe0.8Zn0.2)O3-δ (BLFZ) is a good candidate for protonic ceramic fuel cell cathodes owing to its high proton concentration and decent electronic conductivity. However, the poor catalytic activity of BLFZ limits the electrochemical reaction on the cathode surface, resulting in poor fuel cell performance in hydrocarbon fuels. In this study, to enhance the catalytic activity of BLFZ, Fe cations were substituted with cobalt (Co) cations to synthesize (Ba0.95La0.05)(CoxFe0.8-xZn0.2)O3-δ (BLCFZ) (x = 0–0.8). A single-phase perovskite structure was obtained when the mol% of Co (x) was 0.2 and 0.4, while secondary phases were observed at x = 0.6 and 0.8. The cathode performance was improved by doping Co into BLFZ. The polarization resistances of the fuel cell with BLCFZ (x = 0.2) in H2 and CH4 fuels at 600 °C were smaller than those of the fuel cell with BLFZ (x= 0) and the power density in H2 fuel at 600 °C increased from 0.7 to 0.9 Wcm-2. Equivalent circuit models were used to analyze the contribution of Co in improving the catalytic activity of the cathode.