Synergistic activation of PMS by carbonate and metal-free N-doped carbon for rapid degradation of organic pollutants

Nitrogen-doped carbon materials are efficient metal-free catalysts for activating peroxymonosulfate (PMS) in advanced oxidation processes (AOPs). Herein, a honeycomb-like N-doped porous carbon catalyst (CG2N2) was synthesized via pyrolysis using trisodium citrate, glucose, and 3-amino-1,2,4-triazole (3-AT). This catalyst has a large specific surface area, rich active sites (pyrrolic N, C=O) and excellent electron-transfer ability, and outstanding PMS activation performance for organic pollutant degradation. A striking novelty lies in the unprecedented synergistic effect of naturally ubiquitous carbonate (CO 3 2− ) and CG2N2 for PMS activation, which not only accelerates reaction kinetics but also stabilizes catalytic active sites and reshapes the degradation pathway. Experimental results show that CG2N2 completely degrades 20 mg L −1 phenol within 10 min, and the addition of 10 mM CO 3 2− boosts degradation to 100% removal in only 2 min, with the apparent reaction rate constant soaring from 0.853 to 3.426 min −1 . Meanwhile, CO 3 2− significantly enhances the stability of the catalytic system. Systematic characterization reveals that CO 3 2− accelerates PMS decomposition and reactive oxygen species (ROS) generation, while preserving active sites to stabilize the catalyst. Density functional theory (DFT) calculations verify that CO 3 2− strengthens PMS adsorption on the catalyst surface (adsorption energy reduced from −1.52 eV to −1.67 eV) and weakens the O–O bond, theoretically supporting accelerated reaction kinetics. Another innovative finding is that CO 3 2− drives the system from a radical-dominated pathway to a non-radical electron-transfer pathway dominated by the surface-bound CG2N2/PMS∗ intermediate, reducing matrix interference and enabling selective degradation of phenolic pollutants. CG2N2 also shows broad-spectrum degradation ability toward various phenolic pollutants, with CO 3 2− further enhancing efficiency for most targets. This study breaks through the limitation of conventional metal-free PMS activation systems by utilizing naturally abundant carbonate as a synergistic accelerator, providing a highly efficient, sustainable, and matrix-adaptive strategy for organic pollutant removal in complex water matrices.