Crystalline/amorphous composite interface of CoP@Ni/Fe-P as a boosted electrocatalyst for full water splitting.

Heterojunction materials have become good candidates for electrocatalysts thanks to their unique physicochemical merits. Herein, a crystalline-amorphous CoP@Ni/Fe-P heterojunction is constructed for whole water splitting. Originating from the strong electronic reaction at the amorphous-crystal interfaces, the electron density of Co, Ni, Fe and P is adjusted, which will optimize the adsorption and desorption energy of intermediates for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) and lower the kinetic barrier. The CoP@Ni/Fe-P heterojunction displays overpotentials of 125 and 250 mV to drive a current density of 10 mA cm in 1 M KOH. In addition, the whole water splitting performance requires a cell voltage of 1.56 V to deliver 10 mA cm and shows good stability. This work provides a way to design and prepare transition-metal-based materials with good electrocatalytic activity by constructing a crystalline and amorphous heterojunction.