Oxygen vacancy engineering of BiOBr/HNbO Z-scheme hybrid photocatalyst for boosting photocatalytic conversion of CO.

Photo-chemical conversion of CO 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) and two-dimensional (2D) HNbO nanosheets (HNbO 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/HNbO NS (50%-BiOBr-V/HNbO NS) shows a high CO production yield of 164.6 μmol·g with the selectivity achieves to 98.7% in a mild gas-solid system using water as electron donors. Moreover, the BiOBr-V/HNbO 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 Vs, thus guiding a new way to further enhance CO reduction activity of photocatalyst.