Large-scale controlled synthesis of porous two-dimensional nanosheets for the hydrogen evolution reaction through a chemical pathway.

Molybdenum disulfide (MoS2) is an extensively studied promising non-noble catalyst because of its remarkable performance for the hydrogen evolution reaction (HER). However, the primary factors that affect its catalytic activity have not been analysed comprehensively and quantitatively; this impedes the further design and development of MoS2-based electrocatalysts. Herein, using novel porous MoS2 nanosheets prepared via a controlled and scalable KOH-assisted exfoliation pathway, we methodically studied the contributions of bore edge active sites to the catalytic activity towards the HER. To make the preparation safer, 2H-MoS2 instead of 1T-MoS2 that needs to be prepared with butyllithium has been chosen to synthesize porous MoS2 nanosheets. A comparative study revealed that the overpotential of porous MoS2 nanosheets exhibited an extreme point, which was predominantly due to the different densities of bore edge active sites derived from different quantities of KOH. Amazingly, the HER performance of MoS2 nanosheets experienced the most obvious improvement after these nanosheets were treated with 37.5 wt% KOH. A series of tests and density functional theory calculations were conducted to explain the experimental results, which were consistent with each other. Furthermore, this method has been proven to be universal since porous WS2 and SnS2 nanosheets have been prepared by the same route. This study presents novel insights and reveals a new, controlled, and scalable chemical avenue for programming electrocatalysts based on MoS2 or other layered materials.