Minimizing CO2 emissions by photocatalytic CO2 reduction to CH3OH over Li2MnO3/WO3 heterostructures under visible illumination

Abstract

Photocatalytic CO2 reduction to valuable fuels has proved to be a favourable process to produce renewable energy and reduce CO2 emissions, which mostly depends on designing effective photocatalysts with the rapid separation rate of charge carriers. In this contribution, mesoporous n-n heterojunction Li2MnO3/WO3 nanocomposites were designed via a simplistic sol-gel process for CO2 reduction utilizing visible illumination (λ > 420 nm). XRD and TEM measurements confirmed the synthesized Li2MnO3/WO3 nanocomposite is a monoclinic structure, and its particle size is 25 ± 5 nm. The obtained Li2MnO3/WO3 exhibited narrower bandgap energy (1.74 eV), larger surface area (212 m2g−1), exceedingly visible absorbing, and lower recombination of electron and hole. The yield of CH3OH was determined about 198, 871, 1140, 1550 and 1570 mmolg−1 for bare WO3 and 5%, 10%, 15% and 20% Li2MnO3/WO3 nanocomposites, respectively. These results evidenced that the 15% Li2MnO3/WO3 photocatalyst exhibited the best reduction ability compared to other nanocomposites. The CO2 reduction over 15% Li2MnO3/WO3 photocatalyst achieved a maximal CO2 conversion with the substantially boosted CH3OH, i.e., 1550 mmolg−1 after 9 h, which was enhanced 7.8 folds great than of WO3 NPs. Mesoporous Li2MnO3/WO3 nanocomposites, in comparison with bare WO3 NPs, created more active sites for facilitating CO2 and had a specific electric field to more effectively separate charge carriers. The Li2MnO3/WO3 photocatalyst has superior photostability during the continuous reduction of CO2 for 45 h with no remarkable decrease. The possible direct S-scheme mechanism for electron transfer over Li2MnO3/WO3 photocatalyst with the enhanced CO2 reduction ability was discussed. The present work demonstrates an avenue for building highly effective heterostructure photocatalysts in solar-energy-induced potential applications.