Crystalline/amorphous CoP/MnOx heterostructure derived from phase separation for electrochemical catalysis of alkaline hydrogen evolution reaction

Abstract

The electrochemical water splitting in alkaline media is troubled by the lack of efficient electrocatalysts for hydrogen evolution reaction (HER). Herein, a crystalline/amorphous CoP/MnOx heterostructure is converted from a single-phase bimetallic Co–Mn oxide by phase separation strategy. The CoP/MnOx heterostructure only requires an overpotential of 135 mV to reach 10 mA cm−2 in 1 M KOH, which is lower than that of CoP (184 mV). The interface effect between CoP and MnOx is beneficial to the improvement of HER activity, which is confirmed by means of selective etching of MnOx and infrared spectroscopy. Moreover, the crystal size of CoP phase in the heterostructure is lower than that of the mono-component CoP. Furthermore, the decrease of precursor crystal size will give rise to a decrease in the CoP crystal size of heterostructure. The decline of crystal size results in higher active surface area and greater number of interfaces.