Self-assembly of tannic acid and g-C3N4 into nitrogen-doped hierarchical porous carbon for enhanced PMS activation

The emerging field of persulfate-based advanced oxidation focused on heteroatom-doped carbon catalysts for their tunable catalytic properties and environmental benefits. Here, a novel nitrogen-doped porous carbon catalyst (N-C-T) was synthesized by self-assembling tannic acid with g-C₃N₄ nanosheets, followed by carbonization. The g-C₃N₄ nanosheets played a critical role in forming a nitrogen-rich hierarchical porous structure, significantly boosting PMS activation and enhancing phenol degradation efficiency. The optimized catalyst, N-C-900, showed superior performance, removing 97.6 % of phenol in 30 min with a rate constant of 0.121 min⁻¹, 30 times higher than tannic acid-derived TA-900 catalyst. Surface-bound radicals were identified as the primary reactive species in the N-C-900/PMS system. The enhanced adsorption of PMS and phenol on the surface of N-C-900 was conducive to the generation of surface-bound radicals, thereby accelerating phenol degradation. Furthermore, the N-C-900/PMS system also exhibited good reusability and stability across a pH range of 3.5 to 9.5. This study provides insights into designing nitrogen-doped hierarchical porous carbon catalysts and sheds light on the possible catalytic mechanisms during PMS activation.