Photocatalytic CO2 Conversion of M0.33WO3 Directly from the Air with High Selectivity: Insight into Full Spectrum-Induced Reaction Mechanism.

Natural photosynthesis is a solar light-driven process utilized by plants to convert CO2 and water into carbohydrate molecules. The goal of artificial photosynthesis is the reduction of CO2 directly from air into high purity value-added products at atmospheric pressure. However, its realization, combined with deep mechanism investigation, is a huge challenge. Herein, we demonstrate that hexagonal tungsten bronze M0.33WO3 (M = K, Rb, Cs) series with {010} facets, prepared by a peculiar "water-controllable releasing" solvothermal method, showed excellent full spectrum (UV, visible, and NIR lights)-induced photocatalytic CO2 reduction performance directly from the air at ambient pressure. Particularly, after 4 h near-infrared light irradiation, ca. 4.32% CO2 in the air could be converted into CH3OH with 98.35% selectivity for Rb0.33WO3. The experiments and theoretical calculations unveiled that the introduced alkali metal atom occupied the tunnel of hexagonal structure and donated more free electrons to reconstruct the electronic structure of M0.33WO3, which can enhance the polaron transition, modify the energy band structure, selectively adsorb CO2 rather than O2 from the air, decrease the activation energy of CO2 reaction, and finally make the effective CO2 reduction in the air a reality. This work may provide a new possibility for the practical application of artificial photosynthesis.