Nonradical activation of peroxydisulfate promoted by oxygen vacancy-laden NiO for catalytic phenol oxidative polymerization

Engineering the electronic properties of catalysts to facilitate electron transfer and activation of dynamically stable peroxydisulfate (PDS) offers a promising strategy for efficient remediation of recalcitrant organic pollutants through heterogeneous Fenton-like processes, but also presents challenges due to a lack of facile methods. Herein, we highlight a simple defect engineering strategy that greatly increases the efficiency of PDS adsorption and activation by introducing oxygen vacancies (V-O) into NiO to produce an electron-rich surface. Experimental studies and density functional theory (DFT) calculations confirmed that V-O confined in NiO could successfully cause synergetic effects of lower adsorption energy and more exposed active sites, thus facilitating the bonding with PDS molecules and promoting the reactivity of PDS-NiO complex, giving rise to dramatic enhancement of catalytic performance with removal rate as high as 3.978 mmol(phenol) min(-1) g(NiO)(-1). Mechanistic studies further reveal that the surface-activated PDS-NiO complex mediate oxidative polymerization of phenol (a model pollutant) involved in the generation of phenoxyl radicals and subsequent coupling reactions, providing the potential to convert recalcitrant organic pollutants into value-added products. This work may pave the way toward practical fabrication of highly efficient "defect-type" Fenton-like catalysts, and the present method also provides new opportunities to achieve sustainable wastewater treatment through reuse of organic pollutants.