Nitrogen-rich carbon nitride activated peroxymonosulfate for the efficient photodegradation of 2, 4-dichlorophenol: Performance and mechanism insight

Abstract

Photocatalysis technology combined with advanced oxidation processes based on peroxymonosulfate (PMS) activation reveals great potential to degrade refractory pollutants with environmental-friendly and cost-competitive manners. Graphitic carbon nitride (CN) is regarded as a promising visible-light-driven meta-free catalyst due to its inherent advantages, e.g., cost-effective preparation, facile synthesis method and tunable band gap, while its photocatalytic performance is significantly limited by some critical scientific challenges such as high carrier recombination rate, limited exposure of active sites, and inadequate absorption of visible light. To solve the above key scientific problems, herein, 3, 5-diamino-1, 2, 4-triazole was adopted as nitrogen-rich precursor to prepare a nitrogen-rich porous ultra-thin CN photocatalyst via a simple “one-pot” calcination method. The optimal sample ZCN-30 exhibits superior hydrophilicity and stability, as well as higher contact potential disparity (34.6 mV) in contrast to that of CN (8.1 mV). By visible light coupled PMS activation, 10 mg of ZCN-30 can degrade 96.8 % of 2, 4-dichlorophenol in water within 100 min. The corresponding degradation rate constant are 10.9 and 5.3 times those of CN and ZCN-30 free of PMS. The significant performance improvement comes from specific surface area increasing from 96.75 m² g⁻¹ to 45.03 m² g⁻¹, greatly broadened light absorption, and significantly improved charge behavior. The degradation mechanism was clarified combining radicals capture, ESR, LC-MS and DFT calculation. This research supplies a new reference for simple, low cost, greatly improving the photocatalytic performance of CN, and offers an efficient and environmental-friendly scheme for the removal of refractory pollutants in water.