Phosphorus-doped carbon catalyst with ultralow cobalt content for enhanced peroxymonosulfate activation toward rapid phenol degradation

Non-metal doping provides a route to tune metal sites in carbon catalysts for peroxymonosulfate (PMS) activation. Here, a phosphorus-modified N-doped carbon catalyst with an ultralow cobalt loading (Co2-P1-NC; 0.14 wt% Co) was prepared. Under optimized conditions, the Co2-P1-NC/PMS system removed phenol (Ph) within 2.5 min, with an apparent pseudo-first-order rate constant of 2.068 min −1 . Co-free NC and P-NC showed only limited activity, indicating that Co-containing sites account for most of the catalytic enhancement. Quenching tests, electron paramagnetic resonance (EPR), PMSO probing, in situ Raman spectroscopy, electrochemical measurements, and premixing experiments collectively support the coexistence of radical and nonradical routes, with high-valent Co species and interfacial electron transfer making major contributions under the tested conditions. Density functional theory calculations using representative CoN 4 and CoN 3 P models showed that P substitution made PMS adsorption more favorable (from −2.56 to −3.38 eV), whereas the calculated O–O bond length and Bader charge changed only slightly; the adsorption enhancement is therefore attributed mainly to altered geometry and interfacial electronic interactions. P modification also reduced the measured Co leaching concentration from 0.016 to 0.005 mg L −1 . The catalyst rapidly removed several phenolic pollutants, although activity declined during reuse and was inhibited by carbonate and humic acid. These results demonstrate a promising low-Co catalyst design while identifying stability and water-matrix effects as priorities for further development. Download: Download high-res image (308KB) Download: Download full-size image