Nickel Thiocarbonate Cocatalyst Promoting ZnIn₂S₄ Photocatalytic Hydrogen Evolution via Built-In Electric Field

Cocatalysts play an important role in the field of photocatalysis by providing active sites and reducing reaction barriers to increase the reaction rates. However, efficient cocatalysts usually contain expensive noble metals, such as platinum. It is thus of great significance for practical applications in developing low-cost cocatalysts in photocatalysis. In this contribution, we reported a new cocatalyst nickel thiocarbonate (NiCS₃) of ZnIn₂S₄ photocatalytic hydrogen evolution reaction (HER). It was found that the hydrogen production rate of the NiCS₃/ZnIn₂S₄ composite can reach 15.4 mmol·h^-1·g^-1 under visible light when NiCS₃ is composited with ZnIn₂S₄, which is more than three times that of the HER performance of ZnIn₂S₄ alone. The theoretical calculations suggested that the improvement of HER performance is rooted in the built-in electric fields in the NiCS₃/ZnIn₂S₄ composite. The abundant Ni active sites in the NiCS₃/ZnIn₂S₄ composite not only promote the separation and migration of photoinduced carriers but also allow a suitable Gibbs free energy of adsorbed H* (ΔG_H*). This study indicated that NiCS₃ has great potential to replace noble metals as a promising cocatalyst of ZnIn₂S₄ for photocatalytic hydrogen evolution.