Photocatalytic CO 2 Conversion of M 0.33 WO 3 Directly from the Air with High Selectivity: Insight into Full Spectrum-Induced Reaction Mechanism

Abstract

Natural photosynthesis is a solar light-driven process utilized by plants to convert CO 2 and water into carbohydrate molecules. The goal of artificial photosynthesis is the reduction of CO 2 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 M 0.33 WO 3 (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 CO 2 reduction performance directly from the air at ambient pressure. Particularly, after 4 h near-infrared light irradiation, ca. 4.32% CO 2 in the air could be converted into CH 3 OH with 98.35% selectivity for Rb 0.33 WO 3 . 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 M 0.33 WO 3 , which can enhance the polaron transition, modify the energy band structure, selectively adsorb CO 2 rather than O 2 from the air, decrease the activation energy of CO 2 reaction, and finally make the effective CO 2 reduction in the air a reality. This work may provide a new possibility for the practical application of artificial photosynthesis.