Zn_0.5Cd_0.5Se Embedded CuS 0D/2D S-Scheme Heterojunction for Surface-Plasmon-Resonance Enhanced Photocatalytic H₂O₂ Production and <i>para</i>-Nitrophenol Reduction

Artificial photosynthesis has ignited the spark for significant hydrogen peroxide (H2O2) formation owing to its environmental sustainability and cost-effectiveness; however, limited light absorption potential and sluggish charge separation/migration hinder the overall photocatalytic efficiency. To overcome this, a heterostructure of point-to-face S-scheme heterojunction integrated with the surface plasmon resonance (SPR) effect is demonstrated to exhibit high performance. Herein, we synthesized zero-dimensional Zn0.5Cd0.5Se (ZCSe) QDs decorated on CuS (CS) nanosheets through a two-step pathway. The optimized composite CZ2 exhibited a significant photocatalytic H2O2 production (PHPP) rate of 3.73 mmol g–1 h–1 in the presence of ethanol under visible light, which was higher than that shown by their pristine components, with 0.14% solar to chemical conversion efficiency and surpassed the majority of sulfide/selenide-based photocatalysts. Moreover, the optimum CZ2 heterostructure was exposed to the photocatalytic para-nitrophenol reduction (PNP) and obtained the highest 81% PNP reduction efficiency within 120 min. The photoluminescence, Mott–Schottky analysis, XPS, EPR, and quenching experiments led to a better understanding of the mechanistic detail of photocatalytic activity and the construction of S-scheme heterojunction that preserved the charge carriers with strong redox capacity of both ZCSe and CS. Moreover, the SPR effect of Cu further boosted photocatalytic performances. Furthermore, the loading of ZCSe QD on the CS nanosheet improved the affinity of H+ owing to the more negative zeta potential, which promoted oxygen reduction reaction for PHPP, which occurred through a two-step single electron pathway and exhibited facile stability for up to five cycles. This piece of work sheds light on the development of multifunctional photocatalysts for the production of high-value chemicals.