Sulfur-synergized dual-cobalt anchoring configuration in carbon nitride: Deciphering cooperative mechanisms for boosted peroxymonosulfate activation

Abstract

The synergistic effect of dual-element co-doping exhibits superior advantages over single-element modification in advancing sustainable photocatalytic systems. This study develops a series of cobalt/sulfur co-modified carbon nitride (CoSCN) photocatalysts for enhanced peroxymonosulfate (PMS) activation. Structural characterization reveals that S incorporation induces asymmetric distortion of the carbon nitride (C₃N₄) framework and stimulates electron delocalization, whereas Co atoms establish multiple active sites through a distinctive dual-anchoring configuration, collectively boosting PMS activation. Specifically, the CoSCN-8 + PMS + vis system manifests optimal imidacloprid (IMI) degradation efficacy, with a kinetic constant 11.07 times that of the pristine C₃N₄ counterpart. High-valent Co(IV) and ¹O₂ are corroborated as the predominant contributors, synergistically collaborating with •OH and SO₄•⁻ to drive efficient IMI elimination during CoSCN+PMS + vis processes. Quantitative analysis using the competitive kinetics model further reveals that the oxidation contributions of Co(IV) and ¹O₂ in IMI degradation are 46.2 % and 33.3 %, respectively. Through the integration of photoelectrochemical tests, in situ spectroscopic techniques, and density functional theory (DFT) calculations, the interfacial electron migration dynamics between PMS and CoSCN are systematically elucidated, along with plausible mechanisms for IMI decomposition. Additionally, the potential degradation pathways and transformation intermediates of IMI are identified via LC-MS and Fukui index analyses. The CoSCN+PMS + vis system demonstrates remarkable stability and adaptability across diverse water matrices. This investigation is anticipated to furnish valuable references for the future advancement of practical PMS activation strategies utilizing dual-element-doped catalysts.