Controllable construction of bifunctional sites on Ir@Ni/NiO core/shell porous nanorod arrays for efficient water splitting

Ir-modified Ni/NiO core/shell porous nanorod arrays (Ir@Ni/NiO PNAs) are constructed for efficient alkaline full water splitting via a simple and controllable electro-etching process, where the introduced Ir tunes electronic structure of NiO and builds unique bifunctional Ir-Ni3+ catalytic sites. Specially, the high current density during electro-etching dominates the Ir modification and casting of bifunctional Ir-Ni3+ sites. Ir serves as the active site in a high valence state and cooperates with Ni3+ to catalyze the OER. Meanwhile, Ir promotes the recombination of Had while Ni3+ as the co-catalyst accelerates the cleavage of the H-OH bond, which jointly improve the HER activity. Ir@Ni/NiO exhibits extraordinary overall water splitting performance, with an overpotential of 193.8 mV for OER and 54.7 mV for HER at 10 mA cm−2. Furthermore, the two-electrode cell assembled with Ir@Ni/NiO requires only a low cell voltage of 1.50 V to achieve a current density of 10 mAcm−2, outperforming the commercial IrO2 and Pt. This work blazes the trail for the rational design of water-splitting catalysts and the advancement of alkaline water-splitting for hydrogen production.