Band energy engineering: precise regulation of P-band centers to reasonably construct S-scheme heterojunctions for boosting photocatalytic hydrogen production†

Abstract

It is a challenge to optimize the electronic structure of a photocatalyst through rational design and regulation of its band structure to cooperatively promote the generation of photocatalytic hydrogen. Rational construction of heterojunctions is an effective strategy to address the issue of rapid carrier recombination. In this study, by impregnating Co₂VO₄ nanoparticles on CdS nanorods, a Co₂VO₄/CdS S-scheme heterojunction was successfully prepared. Photoelectrochemical tests, in situ X-ray photoelectron spectroscopy analysis, electron paramagnetic resonance, and density functional theory calculations indicate that the composite photocatalyst significantly improves the separation and transport of electron–hole pairs, confirming the charge transfer mechanism within the S-scheme heterojunction. Concurrently, the incorporation of Co₂VO₄ adeptly shifts the p-band center of sulfur (S) further from the Fermi level. This adjustment increases the filling of the p-orbital anti-bonding state, promotes the desorption of the reaction intermediate H*, and significantly reduces Gibbs free energy, thus greatly improving the hydrogen evolution capacity of the photocatalyst. Compared with a single catalyst, Co₂VO₄/CdS exhibits an obvious electron state density near the Fermi energy level, indicating that the conductivity of the catalyst after the combination of CdS and Co₂VO₄ is significantly improved, which is consistent with electrochemical test results. This study provides a new idea for constructing S-scheme heterostructures while coordinating the p-band center to promote photocatalytic hydrogen evolution.