Rational designing of TiO2-X@Cs3Bi2X9 nanocomposite for boosted hydrogen evolution

Halide perovskites are known as compounds possessing interesting properties, including visible light-induced photoactivity, however, they suffer from instability. Herein, a novel technique for reducing the decomposition rate of halide bismuth-based perovskites Cs3Bi2X9 (X=I, Br, Cl) in the aqueous environment by combining with different types of TiO2 (anatase TiO2-I, anatase/rutile TiO2-B, and rutile TiO2-C synthesized using HI, HBr, and HCl acids, respectively) has been described. The specific type of HX has a notable impact on the crystallinity, morphology, and photocatalytic abilities of TiO2-X and they constitute a reaction environment that allows perovskites to survive the synthesis of TiO2. Studies reveal that TiO2-I is the optimal support material for immobilizing perovskite nanoparticles, owing to its extensive surface area and the synergistic effect it has with Cs3Bi2I9. Adding a small amount of Cs3Bi2I9 to iodine-doped TiO2-I improved the photocatalytic performance in the aqueous environment. As a result, 24.3, 22.5, 22.0, and 13.5-fold improvement in H2 production has been realized with decreasing amounts of Cs3Bi2I9 perovskite (10, 50, 100, and 300 mg). Upon detailed characterization and analysis of photocatalytic properties, it has been suggested that when Cs3Bi2I9 nanoparticles are dispersed within the TiO2-I structure, they can establish a close connection which allows the photogenerated electrons of TiO2-I to be extracted to Cs3Bi2I9, effectively preventing the charge recombination. This study provides a feasible possibility for the photocatalytic application of perovskite-based nanocomposites in the aqueous environment.