Oxygen vacancy engineering of BiOBr/HNb₃O₈ Z-scheme hybrid photocatalyst for boosting photocatalytic conversion of CO₂

Photo-chemical conversion of CO₂ into solar fuels by photocatalysts is a promising and sustainable strategy in response to the ever-increasing environmental problems and imminent energy crisis. However, it is unavoidably impeded by the insufficient active site, undesirable inert charge transfer and fast recombination of photogenerated charge carriers on semiconductor photocatalysts. In this work, all these challenges are overcome by construction of a novel defect-engineered Z-scheme hybrid photocatalyst, which is comprised of three-dimensional (3D) BiOBr nanoflowers assembled by nanosheets with abundant oxygen vacancies (BiOBr-V_O) and two-dimensional (2D) HNb₃O₈ nanosheets (HNb₃O₈ NS). The special 3D-2D architecture structure is beneficial to preventing photocatalyst stacking and providing more active sites, and the introduced oxygen vacancies not only broaden the light absorption range but also enhance the electrical conductivity. More importantly, the constructed Z-scheme photocatalytic system could accelerate the charge carriers transfer and separation. As a result, the optimal BiOBr-V_O/HNb₃O₈ NS (50%-BiOBr-V_O/HNb₃O₈ NS) shows a high CO production yield of 164.6 μmol·g^-1 with the selectivity achieves to 98.7% in a mild gas-solid system using water as electron donors. Moreover, the BiOBr-V_O/HNb₃O₈ NS photocatalyst keeps high photocatalytic activity after five cycles under the identical experimental conditions, demonstrating its excellent long-term durability. This work provided an original strategy to design a new hybrid structure photocatalyst involved V_Os, thus guiding a new way to further enhance CO₂ reduction activity of photocatalyst.