Solar catalytic CO2 reduction over POM-entrapped zeolites decorated with TiO2 nanocomposites in water: Highly efficient and selective production of CH3OH via Z-scheme charge separation

Abstract

Polyoxometalate (POM)-entrapped zeolite Y decorated with AgNTiO2 nanocomposies (AgNTiO2 @POM-Zeolite) were fabricated as inorganic co-photocatalytic systems, and their structures were characterized by XRD, FESEM, TEM, XPS, DRS, and ICPAES analysis. The incident-photon-to-electron conversion efficiency (IPCE) of the thin film of AgNTiO2 @POM-Zeolite was observed to be higher than that of AgNTiO2-POM to confirm the photoinduced charge separation between AgNTiO2 and POM across the zeolites, and its action spectrum was shifted toward longer wavelength to be resolved into two bands as the optical absorption spectrum. The photocatalytic water splitting by AgNTiO2 @POM-Zeolite was also observed to produce O2 with a negligible amount of H2 in contrast to inefficient water splitting by zeolite-free AgNTiO2 nanochains or AgNTiO2-POM, indicating that zeolite plays important role in facile transportation of protons. These results imply that the AgNTiO2 @POM-Zeolite is totally inorganic artificial photosynthetic system for the proton-assisted Z-scheme electron transport between AgNTiO2 nanochains and POM across zeolite surface via stepwise excitation with two visible lights. Accordingly, under simulated solar illumination, the photocatalytic reduction of CO2 in water was observed to show over 95% selectivity of CH3OH and O2 production with much higher conversion rate (240μmol/g cat/h) than ever reported. The newly designed photocatalysts are useful for highly efficient production of solar chemical fuels as well as mitigation of CO2. © 2024