Coupling urchin-like TiO2 nanospheres with nitrogen and sulfur co-doped graphene quantum dots for visible-light-induced degradation of toluene

The development of efficient catalysts for the photocatalytic degradation of volatile organic compounds is paramount. Herein, urchin-like TiO2 nanospheres were coupled with nitrogen and sulfur co-doped graphene quantum dots (NSGDs) through a facile impregnation method. The resulting NSGDs/TiO2 composite forms an S-scheme heterojunction, owing to work function difference, which facilitates the effective separation of photogenerated charge carriers. The NSGDs/TiO2 exhibits an impressive 99.8 % toluene conversion efficiency and 50 % mineralization efficiency during 6 h of visible light illumination. Furthermore, this composite retains its catalytic activity over five consecutive cycles. The remarkable performance is attributed to the augmented visible light absorption and reduced recombination of photogenerated carriers, stemming from the increased electron density of Ti and the establishment of an internal electric field. Photogenerated holes, superoxide radicals, and hydroxyl radicals are identified as the key active species in this process.