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

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.