Photochemical synthesis of bimetallic CuNiS_x quantum dots onto g-C₃N₄ as a cocatalyst for high hydrogen evolution

In the application of graphitic carbon nitride photocatalytic hydrogen production, utilizing transition-metal sulfides instead of noble metals as cocatalysts has broad research prospects. Among them, nickel sulfide is favored by researchers due to its easy preparation, low cost, chemical stability, and excellent photocatalytic performance. Unfortunately, the strong sulfur-hydrogen bonds suppress its development. In this study, we successfully fabricated bimetallic CuNiS_x quantum dots onto graphitic carbon nitride by the photochemical deposition method; such a small size can expose more active S sites on the edge. Simultaneously, the introduction of Cu²⁺ into NiS_x can slightly modulate the electronic structure of Ni and S centers, thus weakening the sulfur-hydrogen bonds. Consequently, the average hydrogen evolution rate of CN/CuNiS_x QDs achieved 1061 μmol h⁻¹ g⁻¹, which is 4.3 times than that of CN/NiS_x QDs (246 μmol h⁻¹ g⁻¹). This research provides a new scenario to design bimetallic sulfide cocatalysts for H₂ evolution.