Synergetic effect of heterojunction and oxygen vacancy on BiOBr/WO3 to enhance the photocatalytic performance of ethyl lactate to ethyl pyruvate

Rational construction of S-scheme heterojunctions with oxygen-vacancy defects represents an effective strategy to mitigate rapid charge recombination and poor photocatalytic selectivity in single-component bismuth‑based photocatalysts. Herein, an oxygen-vacancy-rich BiOBr/WO 3 S-scheme heterojunction photocatalyst was fabricated via a facile coprecipitation method. The well-formed intimate heterointerfaces together with in-situ-generated oxygen vacancies optimize the electronic configuration of the composite, facilitate spatial separation and directional migration of photogenerated carriers, and markedly suppress electron‑hole recombination, thus preserving the strong redox capability of the photocatalyst. Under blue-light irradiation at ambient temperature and pressure, the optimized BiOBr/WO 3 composite achieves superior activity and high selectivity toward the photocatalytic oxidation of biomass‑derived ethyl lactate into ethyl pyruvate. Radical-trapping experiments combined with EPR measurements verify that ·O 2 - and 1 O 2 are the predominant active species, whereas ·OH, carbon‑centered radicals, photogenerated h + and e - synergistically drive the oxidation reaction. These findings systematically reveal the collaborative mechanism governed by multiple active species. This work demonstrates a feasible defect-heterojunction co-design strategy for the efficient selective conversion of biomass-based α -hydroxy esters, and provides valuable insights for developing high‑performance composite photocatalysts.