Novel CoV-LDH/GDY/CuI tandem double S-scheme heterojunction based on graphdiyne (g-C_nH_2n-2) toward photocatalytic hydrogen evolution

Graphdiyne (GDY) is a new two-dimensional carbon hybrid material consisting of sp- and sp2-hybridized carbon networks. In this study, a ternary system of CoV-LDH/GDY/CuI as a double S-scheme heterojunction based on morphology modulation and energy band structure was successfully constructed. We first used an organic total synthesis method to subtly grow GDY on CuI to form a structure of granular CuI wrapped around lamellar GDY. Then, hydrothermally generated CoV-LDH was embedded on GDY/CuI by physical mixing to form an efficient ternary photocatalyst. The transfer path of photogenerated electrons was proved by in situ XPS and the possible reaction mechanism was proposed. The charge transfer and band structure of the catalyst were further verified by density functional theory (DFT) calculations. The results of photocatalytic hydrogen evolution activity showed that the hydrogen evolution activity of ternary CoV-LDH/GDY/CuI photocatalysts was 9.75 and 12.23 times higher than those of CoV-LDH and GDY, respectively. It was further demonstrated that the double S-scheme heterojunction constructed between the photocatalyst components effectively promoted electron separation and transfer, and improved the hydrogen evolution performance of the photocatalysts, providing a new idea for the construction of a rational and efficient photocatalytic system.