Deprivation of unpaired electrons on graphitic carbon nitride-based carbocatalysts by peroxydisulfate driving a nonradical oxidation process

Abstract

This study aimed to seek an effective approach for graphitic carbon nitride (g-C3N4) modification to enhance the non-photocatalytic performance on peroxydisulfate (PDS) activation. Herein, a simple one-step thermal polymerization technique was developed to modulate electronic structures of g-C3N4 by compositing with waste coffee grounds. The formed sandwich-like carbocatalysts (coffee grounds-derived graphitic carbon nitride, Cs/g-C3N4) exhibited an excellent performance on PDS activation toward bisphenol A oxidation via a nonradical pathway. The abundant unpaired electrons around the dangling bonds on the Cs/g-C3N4 surface, which were formed by the mutual substitution of N and C atoms between Cs and g-C3N4 during the annealing process, could be deprived by PDS, forming the reactive electron-deficient carbocatalysts ([Cs/g-C3N4]*) along with a spot of singlet oxygen (1O2) generation to oxidize the organic pollutants. The graphitic N and structural defects might serve as the active sites to offer the unpaired electrons. Compared to singlet oxygen, [Cs/g-C3N4]* revealed a higher mineralization efficiency to reduce the residual ecotoxicity, exhibiting a certain potential in practical applications.