Upgrading Single S-Scheme Heterojunction to Multi-S-Scheme Ones for Better Synergy of Photocatalytic CO2 Reduction and H2O Oxidation: The Third Component Location Matters

Upgrading single S-scheme heterojunctions to multi-S-scheme ones through implanting another component provides a promising means of simultaneously optimizing the charge transport dynamics and surface reaction kinetics, which, however, is challenged by the uncontrollable loading position of the third component. Herein, a component-directed growth strategy is implemented for deliberate deposition of ZnIn2S4 onto diverse locations of In2O3/CdS, constructing twin and triple S-scheme heterojuctions with distinct charge transfer pathways. The photocatalytic performances of as-synthesized ternary heterojunctions in CO2 reduction coupled with H2O oxidation strongly correlate with the location of ZnIn2S4. The selective coating of CdS with ZnIn2S4 expedites the charge transfer and separation, ensures the large-area exposure of In2O3 for smooth H2O oxidation, modulates the reaction energy barriers for promoted CO2-to-CO transformation while suppressing side H2 evolution, and raises the electron density and proton supply for CO2 methanation. Consequently, In2O3/CdS@ZnIn2S4 achieves optimum activities and selectivities in CO and CH4 production, along with nearly stoichiometric O2 evolution. This work not only offers valuable insights for the rational design of three-component heterojunction photocatalysts with multiple S-scheme charge transfer pathways but also opens up a fresh avenue to precisely regulate the loading position of the third component for enhancing the overall efficiency of photoredox catalysis.