Metal-free peroxymonosulfate activation for phenol degradation using selenium–nitrogen co-doped porous carbon nanosheets

Peroxymonosulfate (PMS)–based advanced oxidation processes (AOPs) are promising for pollutant removal, whereas metal-doped carbons risk ion leaching. Here we report a metal-free selenium–nitrogen co-doped porous carbon (Se–N/C) that efficiently activates PMS for phenol (Ph) degradation. Selenium was chosen for its larger atomic radius and high polarizability, which modulate electronic structure and create active sites. Se–N/C achieved complete removal of parent Ph (Ph peak disappearance) within 10 min with a total organic carbon (TOC) reduction of 52 %, and a pseudo-first-order rate constant about twentyfold higher than nitrogen-doped carbon. Radical scavenging tests and electron paramagnetic resonance (EPR) confirm a dual pathway involving radical (O 2 •− ) and non-radical ( 1 O 2 ) species. Density functional theory (DFT) indicates that co-doping tailors the electronic configuration, strengthens PMS adsorption (adsorption energy −3.07 eV), and enhances electron transfer. The catalyst remains active in the presence of common anions (SO 4 2− , Cl − , NO 3 − , and H 2 PO 4 − ) and humic acid, evidencing environmental tolerance. X-ray photoelectron spectroscopy and Raman spectroscopy identify graphitic nitrogen and C–Se–C as key centers, while selenium's antioxidative character supports cycling stability. This work provides a scalable, environmentally benign route for wastewater treatment and clarifies structure–activity relationships in PMS activation.