Unsaturated coordination Cu-doped Ni3S2 enhanced OER activity by promoting in situ surface electro-oxidation

Oxygen evolution reaction (OER) is the key to the electrochemical energy conversion processes. However, limited by sluggish kinetics, it is necessary to find corresponding efficient electrocatalysts for OER to accelerate its reaction speed. Herein, we report a self-supporting electrode using nickel foam (NF) as the substrate to synthesize Cu-doped nickel sulfide nanosheets array on its surface (named Cu–Ni 3 S 2 /NF), which are effective electrocatalysts for OER with low overpotential (270 mV @ J = 50 mA cm −2 ) and small Tafel slope (57 mV dec −1 ). Due to Cu dopant, it could induce the rearrangement of Ni 3 S 2 lattice atoms, resulting in multiple defects and unsaturated metal coordination sites. In addition, it can effectively trigger the surface oxidation of Ni 3 S 2 nanosheets and greatly increase the carrier density near the Fermi level, which remarkably enhances the conductivity. This unique in situ strategy could potentially pave the way for a new generation of electrocatalysts for OER and related energy conversion devices. Graphical abstract