Oriented generation of singlet oxygen in H2O2 activation for water decontamination: regulation of oxygen vacancies over α-MnO2 nanocatalysts

Abstract

The importance of nonradical Fenton-like catalysis in environmental fields has motivated research for effective singlet oxygen (¹O₂) production, but realizing the accurate design and regulation of active sites for manipulating oriented ¹O₂ generation is still highly challenging. In this study, α-, β-, and γ-MnO₂ catalysts with different oxygen vacancy (OV) abundance were fabricated to activate H₂O₂ to generate ¹O₂ for the degradation of oxytetracycline (OTC). The OV-rich α-MnO₂ had a high OTC removal efficiency (>93.5%) at the pH range from 4.0 to 11.0. Moreover, α-MnO₂ exhibited great applicability for a real water matrix, and the total removal of various kinds of emerging contaminants from hospital wastewater reached up to 97.4%. The excellent performances of α-MnO₂ were attributed to the rich contents of OVs that induced the oriented generation of ¹O₂. Theoretical density functional theory (DFT) calculations validated that the OV-rich α-MnO₂ had the highest H₂O₂ adsorption ability (−1.39 eV) and the lowest energy barrier (0.41 eV) for the dissociation of *OH to form the *O intermediate, which promoted the oriented formation of ¹O₂. This work provides a strategy of manipulating the oriented generation of ¹O₂ towards water decontamination via regulating the abundance of oxygen vacancies in α-MnO₂ nanocatalysts.