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 pho-tothermal 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.

Automated summary

In this study, a concentrated photothermal catalysis (CPTC) system was developed to convert light into heat effectively. Mn3O4-based catalysts with unsaturated coordination defects were designed for solar-heating photothermal ethyl acetate oxidation without additional energy input. The Mn3O4-3 catalyst exhibited outstanding photothermal catalytic performance under weak simulated sunlight or natural sunlight irradiation. The enriched unsaturated defects in Mn3O4-3 improved the concentration of surface reactive species and regulated the energy-band structure, leading to enhanced light absorption capacity and charge separation. Experimental and theoretical results showed that the abundant Mn defects promoted the dissociation/hydrolysis of ethyl acetate into key intermediates, while the presence of O vacancies facilitated the dissociation of O2 and deep oxidation of intermediates. The reaction pathway of photothermal ethyl acetate oxidation on manganese oxides under sunlight irradiation was revealed. This work provides an attractive CPTC technology for VOCs removal in energy and environmental applications.