Engineering S-Scheme Heterojunction of Bi 2 S 3 and Zn 0.5 Cd 0.5 Se Quantum Dots for Superior Photocatalytic Activity

High Resolution Image Download MS PowerPoint Slide The photocatalytic O 2 reduction reaction to produce H 2 O 2 has received a lot of attention as a potential approach for energy conversion owing to its economical and sustainable pathway. Here, we have synthesized the Zn 0.5 Cd 0.5 Se (ZCSe)/Bi 2 S 3 S-scheme heterojunction by decorating ZCSe QDs over the Bi 2 S 3 nanoflower. The optimized ZCSe/Bi 2 S 3 (ZB100) composite sample yield was 2.54 mmol g –1 h –1 with ethanol as the sacrificial agent under visible light irradiation, and it was stable for up to four cycles and achieved a solar to chemical conversion efficiency of 0.11% in pure water. The S-scheme mechanism facilitated interfacial charge transfer owing to the interfacial electric field between ZCSe QDs and Bi 2 S 3 . The energy band alignment in the ZCSe/Bi 2 S 3 S-scheme heterojunction was determined from X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, Tauc plot, and Mott–Schottky analysis. The incorporation of Bi 2 S 3 and ZCSe QDs diminished the recombination rate of excitons and enhanced the light absorption capacity. The active radical trapping experiments and NBT test corroborated that superoxide radicals were the dominant intermediate species produced during the H 2 O 2 production reaction following a two-step single-electron pathway.