Engineering Dual-Defective 0D/2D V-CNQDs/V-BiOBr S-Scheme Heterostructure for Boosting CO Photoreduction in Air.

The direct photocatalytic reduction of CO in air is the future trend of photocatalyst application. Herein, the 0D carbon nitride quantum dots with nitrogen vacancies (V-CNQDs) and 2D bismuth-deficient BiOBr (V-BiOBr) are integrated by hydrothermal method. The S-scheme heterostructure of V-CNQDs/V-BiOBr composite promotes the separation rate of photogenerated carriers and enhances the redox capacity. The dual defects provide a large number of adsorption and catalytic sites that enhance the ability to capture and reduce CO. The synergistic effect of S-scheme heterostructure and defect engineering enables the efficiency of CO photoreduction to CO with V-CNQDs/V-BiOBr to reach 16.89 µmol g h in air and 55.69 µmol g h in V: V = 3:1 condition, which is 17 and 21 times higher than that of BiOBr, respectively. The dual-defective V-CNQDs/V-BiOBr exhibits more lower energy barrier for forming CO, COOH, and CO and is easier to release CO gas. And it exhibits excellent cycling stability for photocatalytic CO reduction to CO. The photocatalytic reduction mechanism of CO to CO in the V-CNQDs/V-BiOBr S-scheme heterostructure is further analyzed. This work provides new perspectives for the design of the photocatalysts with defect engineering for efficient photoconversion at low CO concentrations.