Lattice-Matched CoP/CoS₂ Heterostructure Cocatalyst to Boost Photocatalytic H₂ Generation

Transition-metal phosphides and sulfides are considered as promising cocatalysts for the photocatalytic hydrogen evolution reaction (HER), and the cocatalytic effect can be improved by directed heterostructure engineering. In this study, a novel lattice-matched CoP/CoS₂ heterostructure having a nanosheet morphology was developed as an HER cocatalyst and integrated in situ onto graphitic carbon nitride (g-C₃N₄) nanosheets via a successive phosphorization and vulcanization route. First-principles density functional theory calculations evidenced that the construction of the lattice-matched CoP/CoS₂ heterostructure resulted in the redistribution of interface electrons, enhanced metallic characteristics, and improved H* adsorption. As a result of these effects, the CoP/CoS₂ heterostructure cocatalyst formed a 2D/2D Schottky junction with the g-C₃N₄ nanosheets, thus promoting photoelectron transfer to CoP/CoS₂ and realizing fast charge-carrier separation and good HER activity. As expected, the CoP/CoS₂ heterostructure exhibited excellent cocatalytic activity, and the optimal loading of the cocatalyst on g-C₃N₄ enhanced its HER activity to 3.78 mmol g^-1 h^-1. This work furnishes a new perspective for the development of highly active noble-metal-free cocatalysts via heterostructure engineering for water splitting applications.