SnO2 shells-induced rich Co2+ sites and oxygen vacancies in FexCo3-xO4 nanocubes: Enhanced peroxymonosulfate activation performance for water remediation

Cobalt-based heterogeneous composites, as promising peroxymonosulfate (PMS) activators for water remediation, usually suffer from the less reactive sites and metal leakage unfavorable for environmental application. Herein, the well-designed FexCo3-xO4@SnO2 nanocubes are successfully constructed by calcinating Fe-Co prussian blue analogue coated with Sn(OH)Cl. The formation of SnO2 shells preserves the nanocubic microstructure of FexCo3-xO4 to enlarge the specific surface area and induces the generation of rich Co2+ and oxygen vacancy sites on the FexCo3-xO4 surface. The synergy of Co2+ sites and oxygen vacancies contributes to the efficient adsorption and activation of PMS molecules, resulting in the generation of sulfate and hydroxyl radicals as the dominant reactive species for bisphenol A removal. Through adjusting the thickness of SnO2 shells, the optimal composite, FexCo3-xO4@SnO2-2 exhibits the excellent catalytic performance for PMS-involved reaction as compared to the conventional iron/cobalt-based oxides. Moreover, SnO2 shells can effectively inhibit the metal ions leaching during catalytic reaction, which is of great significance for reducing the secondary pollution to water bodies. This study develops a new strategy to regulate the oxygen vacancy sites and inhibit the metal leaching of cobalt ferrites, offering a step forward in the design of high efficient and stable heterogeneous catalysts for water remediation.