Introduction of cobalt vacancies in nickel-cobalt bimetallic oxide hollow multi-shell microspheres for peroxymonosulfate activation: Synergistic interaction of high-valent cobalt-oxygen species with singlet oxygen

Abstract

The strategic engineering of spinel-derived Fenton-like catalysts for persulfate activation via non-radical pathways presents significant potential for advanced water remediation technologies. In this paper, a hollow multi-shell (HMs) catalyst with cationic cobalt vacancy (NiCo^vac/HMs) was designed by combining the sequential template method and strong alkali etching method, and was used for peroxymonosulfate (PMS) activation. The NiCo^vac/HMs/PMS system achieved 95.46 % tetracycline hydrochloride (TCH) removal through dominant ¹O₂ and high-valent cobalt-oxo species (Co(IV)=O) species, contrasting conventional radical-based mechanisms. The synergistic effect between surface Co and Ni improved the electron transport efficiency. In addition, the introduction of Co vacancies optimized the surface electronic structure of the catalyst, which facilitated the adsorption of PMS and the generation of reactive oxygen species (ROSs). The experimental results showed that the NiCo^vac/HMs/PMS system also resisted the interference of humic acid (HA), pH change and inorganic anions, and exhibited good stability and catalytic properties, which has great potential for development in the field of water treatment. This work provided new perspectives for the rational design of spinel catalysts and their use for the activation of PMS, which could contribute to the effective remediation of organic matter pollution in real water bodies.