Oxygen vacant Co3O4in situ embedded on carbon spheres: cooperatively tuning electron transfer for boosted peroxymonosulfate activation

Abstract

Peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) have been regarded as some of the highly promising technologies for degrading pollutants in wastewater. To achieve effective PMS-AOPs, a PMS activator with a fast electron-transfer property for the generation of reactive species is critically important. Herein, carbon spheres embedded with in situ grown oxygen-vacancy-rich cobalt oxide nanoparticles (Co₃O₄@carbon) were synthesised and applied for activating PMS for bisphenol A (BPA) degradation. Systematic characterization, including electron paramagnetic resonance (EPR), synchrotron soft X-ray absorption near edge structure (XANES) and Raman spectroscopy, revealed the presence of both oxygen vacancies and interfacial Co–O–C bonding in the Co₃O₄@carbon composites. The coexistence of oxygen vacancies and interfacial Co–O–C bonds cooperatively accelerated the electron transfer process in the Co₃O₄@carbon/PMS system, as proved by electrochemical studies. Due to the rapid electron transfer induced by the synergy of oxygen vacancies and Co–O–C bonds, the generation of reactive radicals was boosted in the Co₃O₄@carbon/PMS system. Consequently, the Co₃O₄@carbon composite exhibited a superior BPA degradation rate (0.0431 min⁻¹, 100 min) with the superoxide radical as the dominant reactive species. Through surface defect engineering and hybridization with conductive carbonaceous materials, this study provided a new tactic to develop efficient PMS activators towards refractory pollutant degradation in wastewater.