In situ construction of an s-scheme Bi2MoO6/Bi2WO6 heterojunction with dynamic oxygen vacancies for synergistic and efficient photocatalytic CO2 reduction

In photocatalytic CO 2 reduction, it remains challenging to simultaneously achieve efficient separation of photogenerated carriers, preservation of strong redox capability, and surface activation of CO 2 , which constitutes a key bottleneck limiting the reaction efficiency. In this work, a Bi 2 MoO 6 /Bi 2 WO 6 S-scheme heterojunction with intimate interfacial contact and oxygen vacancies was constructed via in situ solvothermal growth to synergistically modulate interfacial charge migration and surface reaction processes. The interfacial charge redistribution upon contact of the two phases establishes a built-in electric field that drives the selective recombination of low-energy carriers, thereby retaining strongly reductive electrons on the Bi 2 WO 6 side and strongly oxidative holes on the Bi 2 MoO 6 side. Meanwhile, oxygen vacancies act as electron trapping and CO 2 adsorption/activation sites, facilitating the formation of key carbon-containing intermediates. In situ spectroscopy, ultrafast carrier dynamics, and theoretical calculations collectively verify the synergistic interplay between S-scheme charge transfer and defect site activation. The optimized 5BWB achieves a CO production rate of 127.2 μmol·g⁻¹·h⁻¹, approximately 6.9 and 6.0 times higher than those of pure Bi 2 WO 6 and Bi 2 MoO 6 , respectively, along with excellent cycling stability. This work demonstrates that the synergistic construction of an interfacial electric field and defective active sites is an effective strategy for reconciling charge separation, strong redox ability, and CO 2 activation.