Efficient activation of peracetic acid by defect-engineered MoO2_x: Oxygen vacancies and surface Mo(V)-mediated electron transfer processes

The role of defect regulation of transition metal catalysts in peracetic acid (PAA) activation is equivocal. To reveal the corresponding mechanism, this work provides a high-efficiency and eco-friendly catalyst (MoO2_x) for PAA activation by introducing various degrees of oxygen vacancies on the MoO2 surface. Interestingly, 95.83 % of tetracycline (TC) is rapidly degraded by MoO 2 _x with rich oxygen vacancies within 20 min via PAA activation, which is superior over that of MoO 2 _x with poor oxygen vacancies and other typical oxidants (H2O2, SO32_, S2O82_, HSO5_, IO4_). In addition, the defect-regulated MoO 2 _x exhibits good de-biotoxicity towards TC. Moreover, MoO 2 _x shows satisfactory purification of various contaminants and actual pharma wastewater. Active species identification suggests that the electron transfer process triggered by the active complex (MoO2_x _PAA*) of PAA bonded on the MoO 2 _x surface plays the dominant role in TC degradation, while center dot OH plays a minor role. Mechanism analysis reveals that oxygen vacancies play an indispensable role in accelerating the adsorption and complexation of PAA as well as improving electrical conductivity. Active site analysis demonstrates that Mo(V) on the MoO2-x surface acts as an electron shuttle and is the main PAA activation site. This work provides a new approach into the application of MoO2 in hospital wastewater purification via defect engineering.