Synergistic activation of peroxymonosulfate by intrinsic defect and graphitic N of N, P co-doped carbon microspheres for BPA degradation

Abstract

Doping nonmetallic heteroatoms into carbonaceous materials is a proven strategy for enhancing peroxymonosulfate (PMS) activation in the degradation of endocrine-disrupting compounds (EDCs). Understanding the role of heteroatom doping defects and intrinsic defects (topological, vacancies, or edge defects) on PMS activation is crucial for designing more efficient carbon catalysts. Herein, we synthesized nitrogen (N) and phosphorus (P) co-doped carbon microspheres (NPCs) through the pyrolysis of aminophosphonic acid resin (D418) precursors and utilized them to activate PMS for bisphenol A (BPA) degradation. The pyrolysis temperature was found to regulate the type and degree of defects, as well as the configuration of N and P. NPC-1000 (pyrolysis temperature at 1000 °C) exhibited the highest reaction rate constant (k) (1.20 × 10−1 min−1) with the lowest N and P doping defects and the highest intrinsic defect intensity resulting from the removal of N and P during pyrolysis. Density functional theory (DFT) calculations and correlation analysis between defect sites and k suggest that the adsorption of PMS was facilitated by graphitic N-coordinated C and intrinsic defect sites rather than P doping defect sites, resulting in the degradation of BPA through electron transfer and radical mechanisms, specifically superoxide radicals (O•–2). Excess halide anions led a significant increase of k with only a limited formation of trichloromethane (TCM) (disinfection byproducts) in presence of 100 mM Cl−. This research offers fundamental insights into constructing intrinsic defects through regulating heteroatom configuration, intending to enhance the catalytic activity of metal-free materials.