Functional Group Modulation in Carbon Quantum Dots for Accelerating Photocatalytic CO2 Reduction

This study investigates the mechanism behind the enhancedphotocatalyticperformance of carbon quantum dot (CQD)-induced photocatalysts. Redluminescent CQDs (R-CQDs) were synthesized using a microwave ultrafastsynthesis strategy, exhibiting similar optical and structural propertiesbut varying in surface functional group sites. Model photocatalystswere synthesized by combining R-CQDs with graphitic carbon nitride(CN) using a facile coupling technique, and the effects of differentfunctionalized R-CQDs on CO2 reduction were investigated.This coupling technique narrowed the band gap of R1-CQDs/CN, madethe conduction band potentials more negative, and made photogeneratedelectrons and holes less likely to recombine. These improvements greatlyenhanced the deoxygenation ability of the photoinduced carriers, increasedlight absorption of solar energy, and raised the carrier concentration,resulting in excellent stability and remarkable CO production. R1-CQDs/CNdemonstrated the highest photocatalytic activity, with CO productionup to 77 & mu;mol g(-1) within 4 h, which is approximately5.26 times higher than that of pure CN. Our results suggest that thesuperior photocatalytic performance of R1-CQDs/CN arises from itsstrong internal electric field and high Lewis acidity and alkalinity,attributed to the abundant pyrrolic-N and oxygen-containing surfacegroups, respectively. These findings offer a promising strategy forproducing efficient and sustainable CQD-based photocatalysts to addressglobal energy and environmental problems.