Stable and high-performance Ir electrocatalyst with boosted utilization efficiency in acidic overall water splitting.

• α-Ni(OH) 2 @Ir core–shell nanoparticles are synthesized at room temperature. • 92 fold better OER mass activity is recorded for α-Ni(OH) 2 @Ir than IrO 2. • α-Ni(OH) 2 @Ir exhibits 5 times higher HER mass activity than Pt/C. The industrialization of solid polymer electrolyte water electrolysis (SPEWE) dominantly relies on electrocatalyst with high stability and efficiency for oxygen evolution reaction (OER) catalysis. In this work, we report a facile method to construct α-Ni(OH) 2 @Ir core–shell nanoparticles as bifunctional electrocatalyst for acidic overall water splitting application. α-Ni(OH) 2 @Ir requires lower overpotentials (238 mV and 20 mV) to achieve 10 mA cm−2 in acidic OER and HER catalysis compared to benchmarked IrO 2 (332 mV) and Pt/C (36 mV); meanwhile, the OER mass activity at 1.55 V vs. RHE was 92 fold higher than IrO 2 ; HER mass activity at overpotential of 80 mV was 5 fold better than Pt/C. The boosted catalytic activity is due to the enhanced utilization efficiency of Ir stemmed from the ultrathin Ir shell (~1 nm). Moreover, 1.49 V is demanded for α-Ni(OH) 2 @Ir to attain 10 mA cm−2 in acidic overall water splitting, 110 mV lower than benchmarked Pt/C-IrO 2 system. Meanwhile, stable catalytic performance is recorded for 20 h. [ABSTRACT FROM AUTHOR]