Enhanced visible light photocatalytic degradation of styrene by g-C3N4 quantum dots/P25 nanocomposites

The enhancement of the visible light response of P25 is of significant importance for the photocatalytic degradation of volatile organic compounds (VOCs). Graphitic carbon nitride quantum dots (CNQD) are nano-sized counterparts of g-C3N4, exhibiting excellent optical properties. Using a simplified hydrothermal one-step approach, CNQD-loaded P25 (CNQD/P25) was obtained in this work. Under visible light, CNQD/P25 achieved styrene degradation rate of 95% within 240 minutes, surpassing the 60% degradation rate of pure P25 under identical conditions. This indicates that the presence of CNQDs greatly enhances the photocatalytic performance of P25 in the visible light region. Further investigations revealed that CNQD/P25 exhibited noticeable enhancement in the ultraviolet-visible absorption spectrum, demonstrating increased visible light absorption. CNQD/P25 demonstrated higher photocurrent response, lower photoresistance, and weaker fluorescence response compared to P25 at similar conditions. Therefore, the presence of CNQDs can enhance visible light absorption of P25, increases the number of photo-generated electrons, optimizes charge separation efficiency, and simultaneously reduces the recombination rate of electrons and holes.