The electrochemical performance of sulfonated silica-supported Pt electrocatalyst investigated as a bifunctional oxygen electrode for unitized regenerative fuel cell (URFC) system. The measured electrochemical surface area values are 23.02 and 22.96 m(2) g(-1) for the Pt black and 80 wt% Pt/SiO2-SO3H catalysts, respectively. The silica support is not prohibiting the electrical conductivity of Pt in the Pt/SiO2-SO3H electrocatalyst due to the high loading of Pt on the supporter. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the fuel cell and water electrolyzer modes were carried out in a unit cell for the Pt/C, Pt/SiO2, and Pt/SiO2-SO3H electrocatalysts. The Pt/SiO2-SO3H catalyst is exhibit better performance in oxygen reduction (hydrogen oxidation) and oxygen evolution (hydrogen evolution) reactions during cyclic processing due to the high proton conductivity of the sulfonated silica supporter. This result means that the sulfonic acid functional group on the support material (SiO2-SO3H) enhances proton conduction in the catalyst layer. Therefore, the ohmic resistance is decrease in the unit cell. Hence, the sulfonated silica supported Pt electrocatalyst is a bifunctional electrocatalyst candidate that can be used in the operation of a URFC. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.