Oxygen migration triggering molybdenum exposure in oxygen vacancy-rich ultra-thin Bi2MoO6 nanoflakes: Dual binding sites governing selective CO2 reduction into liquid hydrocarbons

Oxygen vacancy plays vital roles in regulating the electronic and charge distribution of the oxygen deficient materials. Herein, abundant oxygen vacancies are created during assembling the two-dimensional (2D) ultra-thin Bi2MoO6 nanoflakes into three dimensional (3D) Bi2MoO6 nanospheres, resulting in significantly improved performance for photocatalytical conversion of CO2 into liquid hydrocarbons. The increased performance is contributed by two primary sites, namely the abundant oxygen vacancy and the exposed molybdenum (Mo) atom induced by oxygen-migration, as revealed by the theoretical calculation. The oxygen vacancy (Ov) and uncovered Mo atom serving as dual binding sites for trapping CO2 molecules render the synchronous fixation-reduction process, resulting in the decline of activation energy for CO2 reduction from 2.15 eV on bulk Bi2MoO6 to 1.42 eV on Ov-rich Bi2MoO6. Such a striking decrease in the activation energy induces the efficient selective generation of liquid hydrocarbons, especially the methanol (C2H5OH) and ethanol (CH3OH). The yields of CH3OH and C2H5OH over the optimal Ov-Bi2MoO6 is high up to 106.5 and 10.3 μmol g−1 respectively, greatly outperforming that on the Bulk-Bi2MoO6.