Sulfur doped-graphene for enhanced acetaminophen degradation via electro-catalytic activation: Efficiency and mechanism

Although graphene exhibited excellent performance, its capability of electrochemical catalytic oxidation would significantly improve by modification via sulfur (S)-doping. However, due to the complicated doping species of heteroatoms, the detailed mechanism was still remained open for discussion. Thus, this first-attempt study tended to decipher such mechanism behind the direct and indirect oxidation by analyzing S species in S-graphene. The density functional theory (DFT) was adopted for reactive center calculation and confirmation of secondary active species, to discuss the degradation pathway. As the experimental and calculation results, the thiophene structure S was more favorable for electron acceptation in direct oxidation. Chloride reactive species, as the most effective secondary functionalities (rather than •OH), were favorably generated on the edge doped S position than thiophene structured S in defects, to further trigger the indirect oxidation. However, the extensive contents of reactive functionalities could act as trap for self-annihilation of chloride reactive species, resulting in poor electrocatalytic degradation of the pollutants. This study deepened the understanding of heteroatoms doping for electrochemical catalytic oxidation.