All-Inorganic Perovskite NiTiO 3 /Cs 3 Sb 2 I 9 Heterostructure for Photocatalytic CO 2 Reduction to CH 4 with High Selectivity.

Developing efficient and stable halide perovskite-based photocatalysts for highly selectivity reduction CO 2 to valuable fuels remains a significant challenge due to their intrinsic instability. Herein, a novel heterostructure featuring 2D Cs 3 Sb 2 I 9 nanosheets on a 3D flower-like mesoporous NiTiO 3 framework using a top-down stepwise membrane fabrication technique is constructed. The unique bilayer heterostructure formed on the 3D mesoporous framework endowed NiTiO 3 /Cs 3 Sb 2 I 9 with sufficient and close interface contact, minimizing charge transport distance, and effectively promoting the charge transfer at the interface, thus improving the reaction efficiency of the catalyst surface. As revealed by characterization and calculation, the coupling of Cs 3 Sb 2 I 9 with NiTiO 3 facilitates the hydrogenation process during catalytic, directing reaction intermediates toward highly selective CH 4 production. Furthermore, the van der Waals forces inherent in the 3D/2D heterostructure with face-to-face contact provide superior stability, ensuring the efficient realization of photocatalytic CO 2 reduction to CH 4 . Consequently, the optimized 3D/2D NiTiO 3 /Cs 3 Sb 2 I 9 heterostructure demonstrates an impressive CH 4 yield of 43.4 µmol g -1  h -1 with a selectivity of up to 88.6%, surpassing most reported perovskite-based photocatalysts to date. This investigation contributes to overcoming the challenges of commercializing perovskite-based photocatalysts and paves the way for the development of sustainable and efficient CO 2 conversion technologies.