Uncovering the role of unsaturated coordination defects in manganese oxides for concentrated solar-heating photothermal OVOCs oxidation: Experimental and DFT explorations

In this study, we innovatively develop a concentrated photothermal catalysis (CPTC) system with a cost-effective solar concentrator to efficaciously achieve light-to-heat conversion, and combine a defect engineering strategy to design Mn3O4-based catalysts with unsaturated coordination defects (O and Mn atoms) for solar-heating photothermal ethyl acetate oxidation without additional artificial-energy input. As a result, Mn3O4-3 exhibits outstanding photothermal catalytic performance for ethyl acetate and other OVOCs oxidation under weak simulated sunlight even natural sunlight irradiation. The enriched unsaturated defects in Mn3O4-3 with lower Mn-O and Mn-Mn coordination numbers not only improve the concentration of surface reactive species (Mn4+ and Oads), but also regulate the energy-band structure to further promote the light absorption capacity and charge separation. Experimental and theoretical evidences demonstrate that the generation of abundant Mn defects is conducive to the ethyl acetate dissociation/hydrolysis into key intermediates, while the existence of more O vacancies synergistically facilitates the O2 dissociation toward highly reactive O* participating in the deep oxidation of key intermediates. Moreover, in-situ DRIFTS and DFT results reveal the reaction pathway expansion (Pathway I and II) of photothermal ethyl acetate oxidation on manganese oxides under sunlight irradiation. This work provides an attractive CPTC technology for VOCs removal in energy and environmental application.