Stepwise carbonization of nanocellulose to N-doped carbons with structural transformation and enhanced peroxymonosulfate activation

Metal-free nanocarbons with versatile structural dimensions and unique properties are promising materials for remediation of polluted environment. In this work, a 3-dimensional (3D) interconnected porous N-doped carbon (CN-3) was synthesized by stepwise pyrolysis of dicyandiamide and nanocellulose, and a solid-state-growth and rolling-up mechanism was proposed for the stepwise transformation from stacking layered structures (melem and g-C 3 N 4 ) into CN-3 with 3D interconnected network nano-architectures. It was found that the functional carbons obtained at varying annealing temperature presented different activities in peroxymonosulfate (PMS) activation for endocrine-disrupting chemical (estrone) oxidation, showing temperature-dependent mechanisms from radical-dominated reaction to nonradical oxidation. CN-3 presented 100% estrone removal in 10 min, much higher than the layered carbons. In addition, CN-3 exhibited satisfactory stability during the catalytic reactions. Characterizations indicated that persistent free radicals on the layered carbons tended to induce radical reaction while graphitic structure and N in derived 3D carbons are more responsible for nonradical reaction. This work provides new insights to the relationship between the carbon structural transformation and catalytic PMS activation to induce different oxidative pathways, which facilitate the generation of a highly active and stable carbon-based catalytic system for organic degradation.