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

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.