Synergetic Metal Defect and Surface Chemical Reconstruction into NiCo2S4/ZnS Heterojunction to Achieve Outstanding Oxygen Evolution Performance

Defect and interface engineering are recognized as effective strategies to regulate electronic structure and improve activity of metal sulfide. However, the practical application of sulfide is restricted by their low conductivity and rapid decline in activity derived from large volume fluctuation during electrocatalysis process. More importantly, the determination of exact active site of sulfide is complicated due to the inevitable electrochemical reconstruction. Herein, ZnS nanoparticles with Zn defect are anchored onto the surface of NiCo2S4 nanosheet to construct NiCo2S4/ZnS hybrids, which exhibit outstanding oxygen evolution performance with an ultralow overpotential of 140 mV. The anchoring of defective ZnS nanoparticles inhibit the volume expansion of NiCo2S4 nanosheet during the cycling process. Density-functional theory reveals that the build-in interfacial potential and Zn defect can facilitate the thermodynamic formation of *O to *OOH, thus improve their intrinsic activity.

Automated summary

Defect and interface engineering are effective strategies to improve the activity of metal sulfides, but the practical application is limited by low conductivity and volume fluctuation. By anchoring Zn-defective ZnS nanoparticles on the surface of NiCo2S4 nanosheets, the NiCo2S4/ZnS hybrids exhibit outstanding oxygen evolution performance with an ultra-low overpotential of 140 mV. The anchored ZnS nanoparticles inhibit volume expansion of NiCo2S4 nanosheets during cycling.