Synergistic two- and three-dimensional morphology engineering of pyrite-type CoPS to boost hydrogen evolution over wide pH range

Abstract By designing the morphology and architecture of employed electrocatalysts, the development of high-performance hydrogen evolution reaction (HER) electrocatalysts for electrolytes with a wide pH range is practical significance for future energy conversion technologies. Herein, we synthesize an electrocatalyst composing of two-dimensional (2D) ultrathin ternary pyrite-type cobalt phosphosulfide nanosheets and conductive carbon black (CoPS NSs/C) by the one-step phosphosulfide process. Thanks to the introduction of the C, the composite not only presents a unique three-dimensional (3D) interconnected reticulum structure but also effectively reduces the thickness of nanosheets. The as-synthesized electrocatalyst exhibits remarkable small overpotential toward HER in wide pH range. Meanwhile, the electrocatalyst owns higher charge transfer rate and excellent stability. The good performance is mainly attributed to the combination of the advantages of both 2D nanosheets and 3D interconnected reticulum structure, which offers larger surface area, sufficient active sites and more contaction with electrolytes. This work provides a new method for preparing ultrathin ternary transition-metal phosphosulfide (TMPS) nanosheets, and offers a facile route for improving electrocatalytic activity by designing synergistic morphology of 2D and 3D.