Enhanced Nonradical Co(IV) Formation by Synergistic Cobalt–Iron Sites in <i>g</i> -C ₃ N ₄ for Efficient Peracetic Acid Activation and Decontamination

Peracetic acid (PAA) activation has been considered as a promising technology for emerging contaminant removal in water, while the activity of the catalysts still needs to be developed. In this study, a bimetallic cobalt and iron codoped graphitic carbon nitride (CoFeCN) catalyst was designed to catalyze PAA, where iron was employed as an auxiliary metal to promote Co(IV) generation at cobalt sites. The CoFeCN/PAA system could efficiently remove 95.0% tetracycline, with a pseudo-first-order reaction rate constant of 0.591 min–1, and the catalytic activity of CoFeCN was 2.4 and 4.0 times higher than those of CoCN and FeCN, respectively, under the same operational conditions. Mechanistic investigations identify the primary nonradical pathway dominated by Co(IV) species, and density functional theory calculations suggest that Co(IV) generation is thermodynamically more favorable. The abundant Co(IV) was mainly ascribed to a synergistic effect involving increased Co(II) active sites, introduced iron active sites, accelerated redox cycle of cobalt, and facilitated Co(IV) generation by iron sites adjacent to cobalt. The CoFeCN/PAA system also exhibited promising practical application potential, including efficient degradation of various pollutants, excellent anti-interference capacity, and high efficiency for toxicity reduction. Overall, this study provides a new strategy for abundant Co(IV) generation to effectively and selectively eliminate emerging contaminants.