Oxygen–vacancy-assisted S-scheme interface engineering toward efficient and stable solar hydrogen generation

Although the conduction band position of ZnCdS is thermodynamically favorable for proton reduction, its photocatalytic performance is limited by the rapid recombination of charge carriers and the low efficiency of charge separation. To address this issue, a ZnCdS/OV–CoCeOX heterojunction was constructed. The energy level difference between ZnCdS and CoCeOX drives the formation of an S-scheme heterojunction, promoting directional electron transfer and selective recombination of low-energy holes, and improving the efficiency of electron–hole separation. The oxygen vacancies in CoCeOX capture electrons by creating trap states, delaying recombination and providing unsaturated sites to promote the adsorption and activation of reactants. The synergistic effect of the S-scheme band alignment and the oxygen vacancies enables the effective accumulation of electrons at the active sites, promoting hydrogen production. DFT calculations and experiments confirmed that the redistribution of interface charges dominates the separation of charge carriers and the catalytic performance. After optimization, the composite material containing 20% OV–CoCeOX has an activity 5 times higher than that of a single component. This work reveals the synergistic enhancement mechanism of band matching in S-scheme heterojunctions and oxygen vacancy defects, providing new ideas for the design of efficient heterojunction catalysts.