Hierarchical porous Ni3S4 with enriched high-valence Ni sites as a robust electrocatalyst for efficient oxygen evolution reaction

Abstract

Hydrogen is an environmentally friendly and renewable energy carrier for green energy supply and storage. Hydrogen evolution reaction (HER), as the half reaction of electrochemical water splitting, is one way to produce hydrogen. However, the sluggish kinetics of the oxygen evolution reaction (OER) that is the other half reaction of electrochemical water splitting significantly limits the overall energy conversion efficiency of water splitting. Hence, it is urgent to develop high-efficient electrocatalysts for the OER in order to improve the overall efficiency of electrochemical water splitting. In this work, an active and stable Ni3S4 architecture is designed as an advanced electrocatalyst for OER. The obtained Ni3S4 showed a large nanoflake structure with a uniform distribution of Ni and S, which was proved by electron energy loss spectroscopy (EELS). Meanwhile, the high-resolution transmission electron microscopy (HRTEM) images indicate that the nickel sulphide has a good crystallinity, which is in agreement with the cubic phase of Ni3S4 (space group: Fd3mS). In addition, this sample exhibited a relatively low overpotential of 257 mV at 10 mA/cm2 and had a long-term stability due to the high concentration of Ni3+ and the meso–macro hierarchical porous structure. The water-splitting electrolyzer using the Ni3S4 as the anode catalyst and Pt/C as the cathode catalyst achieves a low cell voltage of 1.51 V at 10 mA/cm2. Therefore, this work provides a new strategy for the rational design of active OER electrocatalysts.