Double S-scheme Cu2−xSe/twinned-Cd0.5Zn0.5S homo-heterojunctions with surface plasmon effects for efficient photocatalytic H2 evolution

The double S-scheme electron transfer pathway of the Cu2−xSe/T-Cd0.5Zn0.5S system leverages the synergistic effect of interface and bulk phase S-scheme homo-heterojunctions, along with the utilization of “hot electrons” generated by the LSPR effect, to facilitate efficient charge separation and transfer, thereby achieving enhanced performance in H2 evolution. [Display omitted] •The twinned-Cd0.5Zn0.5S, composed of zinc blende and wurtzite Cd0.5Zn0.5S have excellent H2 evolution activity.•Cu2−xSe can further promote charge separation and enhance the H2 evolution kinetics.•The Cu2−xSe/T-Cd0.5Zn0.5S homo-heterojunctions with interface and bulk synergistic double S-scheme.•The injection of “hot electrons” generated by the LSPR effect of Cu2−xSe into the T-Cd0.5Zn0.5S. The enhancement of charge separation and utilization efficiency in both the bulk phase and interface of semiconductor photocatalysts, as well as the expansion of light absorption range, are crucial research topics in the field of photocatalysis. To address this issue, twinned Cd0.5Zn0.5S (T-CZS) homojunctions consisting of wurtzite Cd0.5Zn0.5S (WZ-CZS) and zinc blende Cd0.5Zn0.5S (ZB-CZS) were synthesized via a hydrothermal method to facilitate the bulk-phase charge separation. Meanwhile, Cu2−xSe with localized surface plasmon resonance effect (LSPR) generated by Cu vacancies was also obtained through a hydrothermal process. Due to their opposite electronegativity, a solvent evaporation strategy was employed to combine Cu2−xSe and T-CZS by intermolecular electrostatic. After optimization, the photocatalytic hydrogen (H2) evolution rate of 5 wt% Cu2−xSe/T-CZS reached an impressive value of 60 mmol∙h−1∙g−1, which was 4.6 and 66.6 times higher than that of pure Cu2−xSe and T-CZS, respectively. Furthermore, this composites demonstrated a remarkable rate of 0.46 mmol∙h−1∙g−1 under near-infrared (NIR) wavelength (>800 nm). The enhanced performance observed in Cu2−xSe/T-CZS can be attributed to its unique and efficient double S-scheme charge transfer mechanism which effectively suppresses rapid recombination of electron-hole pairs both within the bulk phase and at the surface interfaces; this conclusion is supported by Density Functional Theory (DFT) calculations as well as electron paramagnetic resonance spectroscopy analysis. Moreover, incorporation of Cu2−xSe enables effective utilization ultraviolet visible-near infrared (UV–Vis-NIR) light by the composites while facilitating injection “hot electron