Electronic\nStructure Modulation of Graphitic Carbon\nNitride by Oxygen Doping for Enhanced Catalytic Degradation of Organic\nPollutants through Peroxymonosulfate Activation

Abstract

Oxygen-doped\ngraphitic carbon nitride (O–CN) was fabricated\nvia a facile thermal polymerization method using urea and oxalic acid\ndihydrate as the graphitic carbon nitride precursor and oxygen source,\nrespectively. Experimental and theoretical results revealed that oxygen\ndoping preferentially occurred on the two-coordinated nitrogen positions,\nwhich create the formation of low and high electron density areas\nresulting in the electronic structure modulation of O–CN. As\na result, the resultant O–CN exhibits enhanced catalytic activity\nand excellent long-term stability for peroxymonosulfate (PMS) activation\ntoward the degradation of organic pollutants. The O–CN with\nmodulated electronic structure enables PMS oxidation over the electron-deficient\nC atoms for the generation of singlet oxygen (¹O₂) and PMS reduction around the electron-rich O dopants for the formation\nof hydroxyl radical (^•OH) and sulfate radical (SO₄^•–), in which ¹O₂ is the major reactive oxygen species, contributing to the selective\nreactivity of the O–CN/PMS system. Our findings not only propose\na novel PMS activation mechanism in terms of simultaneous PMS oxidation\nand reduction for the production of nonradical and radical species\nbut also provide a valuable insight for the development of efficient\nmetal-free catalysts through nonmetal doping toward the persulfate-based\nenvironmental cleanup.