S-scheme CeO₂/Cd_7.23Zn_2.77S₁₀-DETA heterojunctions for superior cocatalyst-free visible-light photocatalytic hydrogen evolution

The intensifying global energy crisis, coupled with environmental degradation from fossil fuels, highlights that photocatalytic hydrogen evolution technology offers a promising solution due to its efficiency and sustainability. In this study, we synthesized CeO₂/Cd_7.23Zn_2.77S₁₀-DETA (diethylenetriamine is abbreviated as DETA, and subsequently CeO₂ is referred to as EO, Cd_7.23Zn_2.77S₁₀-DETA is abbreviated as ZCS, and the composite with EO comprising 30% is abbreviated as EO/ZCS) nanocomposites with S-scheme heterojunctions. Under conditions without external co-catalysts and utilizing only visible light as the excitation source, EO/ZCS nanocomposites exhibited outstanding photocatalytic hydrogen evolution activity and remarkable stability, presenting significant advantages over conventional methods that rely on co-catalysts and ultraviolet light. The photocatalytic hydrogen evolution rate of EO/ZCS nanocomposites reached 4.11 mmol/(g·h), significantly surpassing that of EO (trace) and ZCS (2.78 mmol/(g·h)). This substantial enhancement is attributed to the S-scheme charge transfer mechanism at the heterojunctions in EO/ZCS nanocomposites, which effectively facilitates the efficient separation and transfer of photogenerated electron-hole pairs, thereby substantially enhancing photocatalytic hydrogen evolution activity. Through techniques such as X-ray photoelectron spectroscopy (XPS) and theoretical calculations, we confirmed the formation of S-scheme heterojunctions and elucidated their photocatalytic hydrogen evolution mechanism. The results underscore the potential of EO/ZCS nanocomposites as highly efficient and stable photocatalysts for hydrogen production under environmentally benign conditions.