Ni Single Atoms and Ni Phosphate Clusters Synergistically Triggered Surface-Functionalized MoS2 Nanosheets for High-performance Freshwater and Seawater Electrolysis

Two-dimensional metal dichalcogenides have been evidenced as potential electrocatalysts for hydrogen evolution reaction (HER); however, their application is limited by a poor oxygen evolution reaction (OER) activity due to insufficient number/types of multi-integrated active sites. In this study, we report a novel bifunctional catalyst developed by simultaneous engineering of single nickel atoms (Ni-SA) and nickel phosphate clusters (Ni-Pi) to synergistically trigger surface-functionalized MoS2 nanosheets (NSs) resulting in high reactivities for both HER and OER. The Ni-SA-Ni-Pi/MoS2 NSs material exhibits a fairly Pt-like HER behavior with an overpotential of 94.0 mV and a small OER overpotential of 314.0 mV to reach 10 mA cm(-2) in freshwater containing 1.0 M KOH. Experimental results of the catalyst are well supported by theoretical study, which reveals the significant modulation of electronic structure and enrichment of electroactive site number/types with their reasonably adjusted free adsorption energy. For evaluating practicability, the Ni-SA-Ni-Pi/MoS2 NSs-based electrolyzer delivers effective operation voltage of 1.62, 1.52, and 1.66 V at 10 mA cm(-2) and superior long-term stability as compared to Pt/C//RuO2 system in freshwater, mimic seawater, and natural seawater, respectively. The present study indicates that the catalyst is a promising candidate for the practical production of green hydrogen via water electrolysis.

Automated summary

This study reports the development of a novel bifunctional catalyst that enhances the catalytic activity of MoS2 nanosheets for both HER and OER by engineering single nickel atoms and nickel phosphate clusters. The experimental results, supported by theoretical study, demonstrate the practicality and potential of this catalyst for green hydrogen production via water electrolysis.