A new Ni-based cocatalyst nickel thiocarbonate enhancing graphitic carbon nitride photocatalytic hydrogen production by constructing a built-in electric field.

Despite the excellent photocatalytic activity under visible light, graphitic carbon nitride (g-CN) exhibits a high overpotential for hydrogen evolution. To address this issue, cocatalysts have been utilized to modify g-CN. However, the use of high-performance cocatalysts typically involves noble metals such as platinum and palladium, which are cost-prohibitive for practical applications. Therefore, the development of efficient and cost-effective cocatalysts is crucial for advancing photocatalysis. In this study, we synthesized a new Ni-based cocatalyst, nickel thiocarbonate (NiCS), to enhance the photocatalytic hydrogen evolution reaction (HER) on g-CN. The NiCS/g-CN composite demonstrated a significantly increased hydrogen evolution rate of 951 μmol·h·g under visible light, representing more than a 105-fold improvement compared to pure g-CN. Theoretical calculations suggested that the enhanced performance in photocatalytic hydrogen production can be attributed to the generation of a built-in electric field within the composite, facilitating efficient charge carrier separation and migration. Additionally, the C site in NiCS provides a favorable Gibbs free energy of adsorbed H* (ΔG). This work underscores the potential of NiCS as a viable alternative to precious metals in photocatalytic hydrogen production using g-CN.