Spatial confinement and erbium-mediated electronic modulation for enhanced 4-nitrophenol destruction through peroxymonosulfate activation

•Spatial confinement effect of Er/Co@NCB was utilized to enhance 4-NP removal rate.•Er-doping regulated the electronic structure of Co sites for PMS activation.•Synergy of confinement effect and electronic modulation facilitate degradation.•Radical and non-radical pathways contributed to the degradation process. The development of efficient strategies to modulate the electron structure of active sites in heterogeneous catalysts is crucial but remains challenging for enhancing peroxomonosulfate (PMS) activation to degrade organic contaminants. In this study, Co-Er-N-doped carbon black materials are successfully synthesized by pyrolyzing the CB@Er/Co-complex precursor. Er-doping does not enhance the defect level or graphitization degree of the carbon matrix, but rather regulates the electronic structure of Co sites, thereby generating abundant metallic Co species for activating PMS and yield increased reactive oxygen species towards 4-nitrophenol (4-NP) degradation. The optimal Er/Co@NCB-0.6 catalyst exhibits a removal efficiency of 97.9 % in 20 min. Furthermore, this catalyst exhibits broad degradation capabilities against various organic contaminants. Due to the spatial confinement effect from carbon layers, the encapsulated Co nanoparticles in the Er/Co@NCB-0.6 catalyst demonstrate excellent stability and reusability for the reaction. Radical quenching and electron paramagnetic resonance results indicate that the Er/Co@NCB-0.6/PMS system involves radical and non-radical pathways, and 1O2 and SO4•− play essential role in degrading 4-NP. The pollutant is degraded into seventeen intermediates via two plausible pathways. This study provides a valuable rare metal-mediated strategy to regulate the electronic structure of Co-based catalytic materials towards activating PMS in removing persistent organic pollutants.