Ni²⁺ Ion-Induced Phase and Morphology Tailoring in Ni_<i>x</i>–CuMoSe Nanorod Catalysts for Overall Water Splitting

Copper molybdenum-based selenides (CuMoSe) as promising hydrogen evolution catalysts have been widely applied in the electrocatalytic splitting of water, while their limited active sites and relatively poor oxygen evolution activity restrict their further application as effective bifunctional electrocatalysts. Here, we report a simple hydrothermal method to fabricate rodlike NiCuMoSe arrays on nickel foam (Ni_<i>x</i>-CuMoSe/NF), the morphology of which is determined by Ni²⁺ ions because Ni²⁺ can promote the growth of the rodlike structure. Furthermore, the phase transformation from CuSe to CuSe₂ is triggered by adjusting the Ni²⁺ ion content of the growth solution. Due to the morphology control and phase component modulation, the prepared Ni_2.5-CuMoSe/NF possesses effective catalytic activities of the hydrogen/oxygen evolution reaction (HER/OER) with overpotentials of 89/183 mV at 10 mA cm^-2 in 1 M KOH, and the cell (composed of Ni_2.5-CuMoSe/NF as both the cathode and anode) can provide a current density of 10 mA cm^-2 at a low cell voltage of 1.50 V with a stability of 110 h. This work will advance the development of transition metal electrocatalysts for effective overall water splitting.