MOF-derived metal-free N-doped porous carbon mediated peroxydisulfate activation via radical and non-radical pathways: Role of graphitic N and C[sbnd

Abstract

The development of metal-free catalysts with high activity and stability for persulfate activation draws increasing attention due to their promising performance and environmental benignity. Herein, hierarchically porous nitrogen (N)-doped carbon (NC) with merits of highly-dispersed nitrogen, large surface area and controllable structure is synthesized. The as-prepared NC exhibits outstanding performance for peroxydisulfate activation in the degradation of diverse organic pollutants, as well as a wide working pH range of 3–10. Impressively, an annealing strategy can regulate CO and graphitic N contents in NC and their quantitative correlations with the reaction rate constants reveal that the CO and graphitic N in NC are active sites. Furthermore, peroxydisulfate activation by NC involves with three pathways in which the contribution from radicals (SO4−, OH) are comparatively weak and non-radical pathways including singlet oxygen (1O2) and electron transfer are dominant. The contribution of 1O2 is diminishing with delay of reaction while the electron transfer shows the opposite trend. Besides, good recycling performance is achieved by facile re-annealing of NC. This work provides new insights into the reaction mechanism of persulfate catalysis and can guide future catalyst development in advanced oxidation process.