Metal free and efficient photoelectrocatalytic removal of organic contaminants over g-C3N4 nanosheet films decorated with carbon quantum dots

As a typical metal-free semiconductor photocatalyst, a composite photocatalyst comprised of g-C3N4 nanosheets decorated with carbon quantum dots (CQDs/g-C3N4) was synthesized via a simple ultrasonic dispersion self-assembly method. The structure of the photocatalyst was determined by powder X-ray diffraction and transmission electron microscopy. The photoelectrocatalytic properties of the photocatalyst were examined under visible light irradiation for the degradation of methylene blue (MB) and phenol. The results indicate that the photoelectrocatalytic activities of the CQD/g-C3N4 composites are dependent on the CQD loading quantity. The highest photoelectrocatalytic performance observed from the CQD/g-C3N4 composites was a MB degradation of 97.21% after 3 h of irradiation. A photoelectrocatalytic mechanism for the degradation of MB over the CQDs/g-C3N4 was proposed based on the above. Our results provide an invaluable methodology for the design of a highly visible light-responsive photocatalyst based on CQD/non-metallic material and related functional materials. The metal-free photocatalyst is low-cost, shows thermal and chemical stability, and comprises earth-abundant and environmentally friendly materials, and is promising for semiconductor composites and new energy applications.