Roles of oxygen-containing functional groups of O-doped g-C3N4 in catalytic ozonation: Quantitative relationship and first-principles investigation

Graphitic carbon nitride (g-C3N4) with varied oxygen doping levels was fabricated to investigate the quantitative relationship between oxygen-containing groups and activity of catalytic ozonation employing atrazine as a model pollutant. The regulation on both the types and the amounts of different oxygen-containing groups (CO/CO/COOH) were achieved by simply varying the dosage of the oxalate precursor. The regression analysis showed that the increase of CO/CO groups within appropriate range promoted the catalytic activity for ozonation, while the presence of carboxyl groups induced by excessive oxygen doping exhibited adverse effect. Moreover, the corresponding quantitative structure-activity relationships were established. The electron-rich O centers of oxygen doped g-C3N4 (CO/CO) were identified as the active sites for catalytic ozonation, and the enhanced adsorption of ozone on the active sites were substantiated by DFT calculations. This study is believed to shed light upon the roles of different oxygen-containing functional groups in catalytic ozonation by carbonaceous catalysts.