Comparative analysis of g-C3N4 photocatalysts: Mechanisms of peroxymonosulfate activation for efficient pollutant degradation

Abstract

The properties of graphite-phase carbon nitride (g-C₃N₄) catalysts, made of distinct precursors, exhibit significant differences in microstructure and photocatalytic performance. However, systematic studies on their effectiveness in activating peroxymonosulfate (PMS) for pollutant degradation remain limited. Three different kinds of g-C₃N₄ photocatalysts—CNM, CND, and CNT—were produced in this study by pyrolyzing melamine, dicyandiamide, and thiourea, respectively. Notably, CNM exhibited high crystallinity, reduced layer spacing, and abundant nitrogen defects, contributing to a decreased recombination rate of photogenerated electrons and enhancing its photocatalytic performance. CNM activated PMS with remarkable efficiency, accomplishing a degradation rate of 95.8 % in the PMS/Light system, significantly higher than when CNM and PMS were used separately. Quenching experiments indicated that the primary active species were superoxide radicals (•O₂⁻), singlet oxygen (¹O₂), and photogenerated holes (h⁺) during degradation. Furthermore, CNM demonstrated excellent catalytic activity and stability across various pH levels and in complex environments with various inorganic anions, highlighting its strong resistance to interference. For developing low-cost and stable photocatalysts for organic wastewater degradation, this study presents an advanced approach.