Oxygen vacancy-enhanced magnesium-doped ferrous molybdate photocatalytic-peroxymonosulfate synergistic degradation of pollutants

Mg-doped FeMoO4 composites (labeled Mg/FeMoO4) enriched with oxygen vacancies were prepared and applied in the photocatalytic-peroxymonosulfate synergistic degradation of phenol. The results showed that the 5% Mg/FeMoO4 composites could completely degrade phenol (20 ppm) after 20 min, with a 2.7-fold increase in the synergistic degradation rate constant compared to that of FeMoO4. Experimental results show that Mg doping effectively improved the charge separation efficiency while favoring the formation of surface oxygen vacancies. The presence of oxygen vacancies can promote photogenerated electron-hole separation, accelerate the valence transition of Fe2+/Fe3+, and improve the activation efficiency of PMS. On the other hand, oxygen vacancies can also act as PMS adsorption activation sites to decompose and generate more active species, which is conducive to promoting synergistic degradation activity. Quenching experiment and Electron Paramagnetic Resonance (EPR) results demonstrate that active free radicals (·SO4−, ·OH and ·O2−) and non-free radicals (1O2) play significant roles in the reaction process. Based on this, an oxygen vacancy-enhanced synergistic degradation mechanism is proposed, which provides ideas for the coupling of advanced oxidation technologies as well as the design of catalytic materials to improve pollutant degradation performance.