Designed of dual direct band gap graphdiyne/Co2VO4 S-scheme heterojunction: Enhance the bonding stability of Co active sites to promote photocatalytic hydrogen evolution.

[Display omitted] • High carrier migration efficiency of the double direct bandgap S-scheme heterojunction is obtained. • Strong intrinsic electric fields promote efficient separation and migration of photogenerated charges. • Graphdiyne effectively regulate the d-band center of Co atom. • Introducing graphdiyne effectively increases electron state density at the Fermi level in Co 2 VO 4. The selection of direct band gap semiconductors with high-efficiency electron transitions and the rational adjustment of the d-band center of transition metal atoms can effectively enhance photocatalytic hydrogen evolution. Based on this premise, the double direct band gap graphdiyne/Co 2 VO 4 S-scheme heterojunction was designed via an immersion method. DFT calculation, in-situ XPS and EPR analysis not only provided support for the formation of graphdiyne /Co 2 VO 4 S-scheme heterojunction but also demonstrated that Co maybe served as the most efficient active site for hydrogen evolution. Furthermore, the design of S-scheme heterojunction effectively prolongs the carrier lifetime of the photocatalyst, resolves the deficiency in high electron-hole pair recombination rate of direct band gap semiconductors, and maintains its efficient electronic transition. PDOS analysis revealed that the interaction between graphdiyne and Co 2 VO 4 at the microscopic interface tends to modulate the d-band center of cobalt atoms, resulting in a decrease in electron occupation on antibonding orbitals and consequently enhancing bonding stability at Co active sites. Moreover, introducing graphdiyne effectively increases electron state density near the Fermi level of Co 2 VO 4 , facilitating rapid migration of photogenerated charges. This study provides valuable insights into the regulating d-band centers of transition metal and the development of double direct band-gap S- scheme heterojunctions. [ABSTRACT FROM AUTHOR]