Noble-metal-free dual CuNi single-atom embedded in ultrathin ZnIn2S4 for efficient photocatalytic H2 evolution

Developing noble-metal-free dual-metal single-atom catalysts with rich active accessible sites and excellent catalytic activity is very meaningful and challenging, especially for photocatalytic hydrogen production reaction, which can significantly reduce the cost of photocatalytic technology application while reducing the use of noble metals. Herein, a novel noble-metal-free dual CuNi single-atom modified ZnIn2S4 (CuNiSA-ZIS) photocatalyst with high hydrogen production performance were successfully prepared by a hydrothermal method. The ZnIn2S4 with a spherical nanoflower structure is composed of ultrathin nanosheets, and ACHDDAF-STEM results shows that CuNi bimetallic particles are uniformly distributed on the surface of ZnIn2S4 nanosheets and exhibit atomic level dispersion, forming dual-metal single-atom structure. The optimized 1 wt% CuNiSA-ZIS photocatalyst with the Cu/Ni ratio of 1:1 shows the optimum H2 evolution performance with a rate of up to 7844.7 μmol·g−1·h−1 using triethanolamine as a sacrificial reagent, which is significantly improved compared to pristine ZIS, Cu-ZIS and Ni-ZIS samples under simulated sunlight. Electrochemical and spectroscopic characterization results demonstrated that the improved photocatalytic activity of CuNiSA-ZIS was mainly due to the addition of the dual CuNi single atoms with a synergistic effect served as a co-catalyst for ZnIn2S4 photocatalysts, providing efficient active sites for hydrogen evolution while preventing the fast recombination of photo-generated electrons and holes. This study provides a valuable source of ideas for the design of effective noble-metal-free dual-metal single-atom catalysts.