Co–P bond effect on an MOF-derived Co9S8 hollow polyhedron supported Ni2P co-catalyst for efficient photocatalytic hydrogen evolution

Abstract

The development of new, efficient noble-metal-free photocatalysts is of great significance for the photocatalytic hydrogen evolution reaction. Herein, Co₉S₈ with a hollow polyhedral structure was synthesized by in situ sulfurization of ZIF-67, and subsequently, Co₉S₈@Ni₂P composite photocatalytic materials were prepared by loading Ni₂P on the surface of Co₉S₈ through a solvothermal method based on a morphology regulation strategy. The design of the 3D@0D spatial structure of Co₉S₈@Ni₂P is favorable for the formation of photocatalytic hydrogen evolution active sites. Due to the excellent metal conductivity of Ni₂P, Ni₂P as a cocatalyst can accelerate the separation of photogenerated electrons from holes in Co₉S₈, thus providing a large number of available photogenerated electrons for photocatalytic reactions. It is worth mentioning that a Co–P chemical bond is formed between Co₉S₈ and Ni₂P, which plays an active role in the transport of photogenerated electrons. The densities of states of Co₉S₈ and Ni₂P were determined by density functional theory (DFT) calculations. The reduction of the hydrogen evolution overpotential and the formation of efficient charge-carrier transport channels on Co₉S₈@Ni₂P were confirmed by a series of electrochemical and fluorescence tests. This study provides a new idea for the design of highly active noble-metal-free materials for the photocatalytic hydrogen evolution reaction.