Low-loading IrO2 supported on Pt for catalysis of PEM water electrolysis and regenerative fuel cells

A unitized regenerative fuel cell (URFC), an electrochemical device operated in both water electrolysis (WE) and fuel cell (FC) modes, is a promising technology in interconverting renewable electricity and chemical fuels within a compact system. However, Proton-exchange membrane-based URFCs usually employ a significant amount of precious metal catalysts, e.g., up to 4 mg((Pt+IrO2)) cm(-2), to achieve high efficiency in round-trip operations. Here, we present a PEM-URFC electrode that uses only 0.8 mg((Pt+Ir)) cm(-2) without compromising the performance of URFC. IrO2-shells (70 nm) layered upon hemispherical Pt particles (Pt@IrO2) are formed using sequential electrodeposition over Ti-felt electrodes. A 100 % improvement in WE compared to performance without Pt supports and superior mass activity (44 A mg(Ir)(-1) at 2 V-cell) with an insignificant degradation rate of 155 mu V h(-1) at 0.4 A cm(-2) are demonstrated. In addition, high round-trip efficiency of 49 % at 0.4 A cm(-2) in URFC is achieved.