Hierarchical Hollow TiO₂@Bi₂WO₆ with Light-Driven Excited Bi^(3–x)+ Sites for Efficient Photothermal Catalytic CO₂ Reduction

Converting CO₂ into valuable chemicals via sustainable energy sources is indispensable for human development. Photothermal catalysis combines the high selectivity of photocatalysis and the high yield of thermal catalysis, which is promising for CO₂ reduction. However, the present photothermal catalysts suffer from low activity due to their poor light absorption ability and fast recombination of photogenerated electrons and holes. Here, a TiO₂@Bi₂WO₆ heterojunction photocatalyst featuring a hierarchical hollow structure was prepared by an in situ growth method. The visible light absorption and photothermal effect of the TiO₂@Bi₂WO₆ photocatalyst is promoted by a hierarchical hollow structure, while the recombination phenomenon is significantly mitigated due to the construction of the heterojunction interface and the existence of excited Bi^(3–x)+ sites. Such a catalyst exhibits excellent photothermal performance with a CO yield of 43.7 μmol h^–1 g^–1, which is 15 and 4.7 times higher than that of pure Bi₂WO₆ and that of physically mixed TiO₂/Bi₂WO₆, respectively. An in situ study shows that the pathway for the transformation of CO₂ into CO over our TiO₂@Bi₂WO₆ proceeds via two important intermediates, including COO^– and COOH^–. Our work provides a new idea of excited states for the design and synthesis of highly efficient photothermal catalysts for CO₂ conversion.