Up-conversion effect boosted the photocatalytic CO2 reduction activity of Z-scheme CPDs/BiOBr heterojunction

The hunt for novel methods and nanomaterials with suitable band gaps is a critical hindrance to the rational design of Z-scheme heterogeneous junctions, which simultaneously improve the charge transfer efficiency and maintain high redox activity. In this study, a Z-scheme carrier migration system was constructed by uniformly loading carbonized polymer dots on BiOBr nanosheets (CPDs/BiOBr) through a low-heating solid-state chemical reaction. Without the addition of a sacrificial agent or photosensitizer, the photocatalytic reduction rate of a 6 wt% CPDs/BiOBr heterojunction was 144.6 μmol g−1 h−1, which is 2.02 times higher than that of pure BiOBr. The excellent photocatalytic performance of the 6 wt% CPDs/BiOBr composite was attributed to the Z-scheme heterojunction, which can maintain the redox ability of the material and promote the rapid separation of photogenerated carriers. Besides, the up-conversion characteristics of CPDs can broaden the scope of light absorption. This study provides a clear understanding of the role of carbon-based quantum dots in the design of efficient Z-scheme photocatalysts for CO2 reduction.