Engineering Built‐In Electric Field Microenvironment of CQDs/g‐C3N4 Heterojunction for Efficient Photocatalytic CO2 Reduction

Abstract Graphitic carbon nitride (CN), as a nonmetallic photocatalyst, has gained considerable attention for its cost‐effectiveness and environmentally friendly nature in catalyzing solar‐driven CO2 conversion into valuable products. However, the photocatalytic efficiency of CO2 reduction with CN remains low, accompanied by challenges in achieving desirable product selectivity. To address these limitations, a two‐step hydrothermal‐calcination tandem synthesis strategy is presented, introducing carbon quantum dots (CQDs) into CN and forming ultra‐thin CQD/CN nanosheets. The integration of CQDs induces a distinct work function with CN, creating a robust interface electric field after the combination. This electric field facilitates the accumulation of photoelectrons in the CQDs region, providing an abundant source of reduced electrons for the photocatalytic process. Remarkably, the CQD/CN nanosheets exhibit an average CO yield of 120 µmol g−1, showcasing an outstanding CO selectivity of 92.8%. The discovery in the work not only presents an innovative pathway for the development of high‐performance photocatalysts grounded in non‐metallic CN materials employing CQDs but also opens new avenues for versatile application prospects in environmental protection and sustainable cleaning energy.