A composite electrode in protonic ceramic fuel cells (PCFCs) is composed of an ionic conductor, an electronic conductor, and catalysts. To determine the contribution of the properties of the ionic conductor to the electrode performance, three different proton conductors: Ba(Ce0.75Y0.15)O3-delta (BCY), Ba(Ce0.45Zr0.30Y0.15)O3-delta (BCZY), and Ba(Zr0.75Y0.15)O3-delta (BZY), were used to fabricate composite electrodes for PCFCs. Moreover, their effects on the anode and cathode performances were investigated systematically. In the cathodes, the BCZY and BCY scaffolds showed a better performance than the BZY scaffold. However, in the anodes, the BZY scaffold showed a superior performance to the BCZY or BCY scaffold. This exhibited that the requirements of ion-conducting scaffolds in composite electrodes were different in cathodes and anodes and that the fuel cell performance could be optimized by choosing appropriate ionic conductors for each electrode. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.