Robust Polydopamine-Derived Co and N Co-Doped Carbon Nanospheres for Synergistic Radical/Non-Radical Activation of Peroxymonosulfate toward Efficient Antibiotic Detoxification

Abstract

The development of high-performance, yet easily synthesizable cobalt–nitrogen codoped carbon catalysts is pivotal for advancing peroxymonosulfate (PMS)-based advanced oxidation processes. Herein, we report a controllable synthesis of Co/N codoped carbon nanospheres (CoNC) with coexisting atomic Co sites and metallic Co nanoparticles using polydopamine as a versatile precursor, enabling precise tuning of cobalt loading and pyrolysis temperature. The optimized catalyst, CoNC-8-900, possesses a mesoporous architecture, a high specific surface area (492.21 m2 g–1), and coexisting cobalt valence states (Co0, Co2+, Co3+). The catalyst achieved 92.28% tetracycline (TC) degradation with a rate constant of 0.12 min–1. Systematic mechanistic studies unveil that the degradation proceeds via a synergistic radical and nonradical pathway. The radical pathway primarily involves the generation of hydroxyl (•OH) radicals via the Co2+/Co3+ cycle. The nonradical pathway is not solely dependent on singlet oxygen (1O2) but is dominated by a direct electron transfer process (ETP) mediated by the conductive nitrogen-doped carbon matrix and carbon defects. Furthermore, the degradation pathways were delineated, and ecological toxicity assessment verified the effective detoxification of the treated solution. This work not only presents a straightforward strategy for crafting efficient carbon-based catalysts but also provides fundamental insight into the multimechanism activation of PMS for sustainable water purification.