Selective oxygen vacancy engineering for shrinking the potential barrier of S-scheme heterojunction toward highly efficient photocatalytic CO₂ conversion

The construction of S-scheme heterojunction represents a simple yet effective strategy for enhancing photogenerated charge carrier separation and optimizing the reduction and oxidation capability of the photocatalytic system. However, precise tuning of the internal electric field for optimizing charge carrier migration across the heterojunction remains challenging. Herein, we present a novel defect engineering approach to modulate the potential barrier in S-scheme heterojunctions through strategic oxygen vacancy introduction. Specifically, we first selectively introduce oxygen vacancies on Bi₂WO₆, followed by coupling with g-C₃N₄ to form oxygen-deficient Bi₂WO₆/g-C₃N₄ (OVs-BWO-CN) S-scheme heterojunction. Surprisingly, the selective oxygen vacancy engineering on OVs-BWO cannot only preserve the features of common oxygen vacancies, but also shrink the potential barrier formed between OVs-BWO and CN. This reduction in potential barrier facilitates enhanced charge carrier migration across the heterojunction interface. As a direct consequence of this optimized charge transfer, the CN/OVs-BWO heterojunction demonstrates exceptional photocatalytic CO₂ conversion performance, reaching a CO production rate of 48.65 μmol h⁻¹ g⁻¹. Such a work on selective oxygen vacancy engineering for optimizing potential barrier can provide important guidelines for photocatalysis.