Dual-Confinement Engineering of Co@Carbon Core–Shells within N-Doped Hollow Carbon Fibers for •O2– and ETP Dominated Peroxymonosulfate Activation

Abstract

A dual-confinement strategy integrating spatial and chemical confinement is developed to fabricate cobalt- and nitrogen- doped hollow carbon fibers with embedded Co@carbon core–shells (CoN-HCNFs) for efficient peroxymonosulfate (PMS) activation. The spatial confinement of ZIF-67 within polystyrene fibers prevents cobalt agglomeration during pyrolysis, while the polydopamine-derived carbon shell chemically stabilizes active species and promotes abundant Co–Nx site formation. The optimized CoN-HCNFs-800 catalyst features a high specific surface area (462.62 m2 g–1), well-developed mesoporosity (∼3.80 nm), and superior electron transfer capability, achieving 90.74% tetracycline (TC) degradation within 30 min with an apparent rate constant of 0.132 min–1. Mechanistic investigations reveal that the degradation process is governed by a synergistic combination of radical and nonradical pathways, with superoxide radicals (•O2–, 65.15%) and the electron transfer process (ETP, 47.73%) serving as the dominant contributors. The dual-confinement architecture effectively suppresses cobalt leaching, ensures outstanding cycling stability (84.10% after four cycles, recoverable to 92.79% via thermal regeneration), and steers the reaction mechanism toward a •O2– and ETP dominated synergistic PMS activation. Toxicity assessments (ECOSAR and mung bean phytotoxicity) confirm significantly reduced ecological risk of the treated solution. This work establishes dual-confinement engineering as a paradigm for designing durable, nonradical-pathway-oriented catalysts for antibiotic wastewater remediation.