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

[Display omitted] •IrO2 supported on Pt having a hemispheric core-shell structure was constructed to be used as OER and HOR electrode for URFC.•Significant performance, 7.1 A cm−2 at 2.0 Vcell, was achieved in PEMWE with only 0.16 mgIr cm−2 including a stability demonstrated for 220 h.•49% of round trip efficiency at 0.4 A cm−2 was achieved in PEM-URFC with 0.83 mg(Pt+Ir) cm−2 of total noble catalysts. 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 mgIr−1 at 2 Vcell) with an insignificant degradation rate of 155 μV 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.