Surface oxygen vacancy enhanced the activation of peroxymonosulfate on α-Ni0.2Fe1.8O3 for water decontamination: The overlooked role of H2O in interface mechanism

Oxygen vacancies (OVs)-rich α-Ni0.2Fe1.8O3 with dual metal sites was synthesized by Ni2+ isomorphously substituted α-Fe2O3 to activate peroxymonosulfate (PMS) for aceclofenac (ACF) degradation. A novel insight was proposed for the overlooked role of H2O in the surface-complexed process between PMS and unsaturated metal sites induced by OVs. The surface-bond SO4∙- and ∙OH were demonstrated as the dominant reactive oxygen species (ROS). In situ ATR and Raman spectra revealed the reaction of HSO5- with the surface metal sites by replacing the surface-bonded -OH. The DFT study revealed the spontaneous formation of hydrolyzed -OH on OVs (∆G=-1.45 eV), which was further replaced by HSO5- to complex with metal sites (∆G=-3.58 eV). The OⅠ of the H-OⅠ-OⅡ-SO3- was more readily bonded with the Ni or Fe sites around OVs, causing the O-O cleavage for SO4∙- generation. This study proposed a brand-new perspective for the interfacial behavior of PMS activation.