Synergistic effect of oxygen vacancies and S-scheme charge transfer mechanism in 0D/1D CdS/MoO_3-x heterojunction for efficient photocatalytic hydrogen production coupled with highly selective benzyl alcohol oxidation

Constructing an S-scheme heterojunction is a wise strategy to promote the separation of photogenerated carriers in photocatalysis, while efficient charge transfer of the S-scheme heterojunction is governed by the intimate interfacial contact of constructing photocatalysts. In this work, an S-scheme heterojunction photocatalyst was developed by anchoring cadmium sulfide nanoparticles on molybdenum oxide nanowire with oxygen vacancies (0D/1D CdS/MoO_3-x), and was demonstrated to exhibit efficient co-production of hydrogen and high-value chemicals, with an apparent quantum efficiency of 31.2% for hydrogen production in the absence of noble-metal cocatalyst and selectivity of 99.95% for benzaldehyde generation. Comprehensive characterization and theoretical analysis demonstrated that the excellent photocatalytic performance originated from the synergistic interaction between oxygen vacancies and the S-scheme heterojunction. Specifically, the introduction of oxygen vacancies significantly enhanced the strength of the built-in electric field established and facilitated the local charge redistribution at the S-scheme interface, promoting the rapid migration of photogenerated carriers for efficient hydrogen production. Moreover, oxygen vacancies in MoO_3-x provided improved electron-accepting ability, thereby promising highly selective benzaldehyde generation by promoting the adsorption and desorption of active intermediates from benzyl alcohol. This work provides valuable insights for enhancing the efficiency of photocatalytic hydrogen production coupled with the selective conversion of high-value organic compounds.