Ball-milled Ni2P/g-C3N4 for improved photocatalytic hydrogen production

Transition metal phosphides (TMPs) are ideal candidates to replace precious cocatalysts for photocatalytic hydrogen evolution reaction (HER). Understanding the structure-activity relationships between TMPs and the host photocatalysts is an important criterion for the development of highly active TMPs for HER. In this work, the relations were explored with Ni2P and g-C3N4 as prototypes. Ni2P with a clear composition and structure was prepared first by a mild solvothermal method and was then loaded on g-C3N4 with an exact content through a ball milling process. The effects of the modification of Ni2P on g-C3N4 structure, absorption, texture, HER activity, and photo-electrochemical properties were investigated. The results demonstrated that the crystal structure and the texture of g-C3N4 are less impacted by the decoration of Ni2P, but the HER activity can be substantially improved. g-C3N4 modified with 3% Ni2P showed the highest HER performance and it is ca. 9 times higher than the pristine g-C3N4 even Ni2P was loaded just by a simple ball milling process. Ni2P played a dual role as trapping sites to capture photoinduced electrons and the reactive centers to trigger the evolution of hydrogen for its high work function and the low HER overpotential. This work reveals some reliable structure-activity relationships between Ni2P and g-C3N4 and offers a simple approach to synthesize highly efficient Ni2P and its loading on host photocatalyst for enhanced HER.