Degradation of organic pollutants by Co3O4-mediated peroxymonosulfate oxidation: Roles of high-energy {001}-exposed TiO2 support

Co3O4-mediated heterogeneous activation of peroxymonosulfate (PMS) is an efficient strategy to generate sulfate radicals for environmental pollutants degradation. The rate-limiting step is Co-OH- complex formation, and it highly depends on the thermodynamic capacity of water dissociation to generate surface hydroxyl groups. Herein, for efficient PMS activation and pollutants degradation, the water dissociation capacity of TiO2, a promising Co3O4 support, was facilely refined by its shape-tailored synthesis with dominant high-energy {0 0 1} facet. The polar {0 0 1} facet is characterized by a high density of atomic steps, edges and kinks of the low-coordinate surface atoms with a large number of dangling bonds, all of which can serve as reactive sites for water adsorption and dissociation and thus improve Co-OH- complex formation dynamics in sulfate radical formation. Co3O4 deposited on TiO2-{0 0 1} exhibited a much higher PMS activation capacity and pollutants degradation efficiency, i.e. p-nitrophenol and rhodamine B, and a much lower Co2+ leaching. This superiority could be mainly attributed to the strong Ti-5c-centered water adsorption and dissociation, the high density of surface hydroxyl groups, the robust Co-OH- complex generation and the intimate catalyst-support interactions. Our findings might provide a new chance to refine Co-mediated sulfate radical generation and other Fenton-like systems for advanced water treatment with reduced secondary pollution.