In situ preparation of imidazolyl ionic liquid molecular cation moisture-resistant A3Bi2I9 perovskite crystals for efficient photocatalytic water purification and hydrogen production

Abstract

Bismuth-based halide perovskites are semiconductors that respond well to light and can be used in reactions triggered by visible light. However, their structure makes them unstable in wet or aqueous conditions, limiting their use in water-based reactions. This paper presents a new method to create two moisture-resistant bismuth-based perovskites, (1,3-diethylbenzimidazole)₃Bi₂I₉ and (1-Methyl-3-ethyl-benzimidazole)₂(1,3-diethylbenzimidazole)Bi₂I₉, by using N-methylbenzimidazole and N-ethylbenzimidazole with bismuth iodide. During this process, ethanol molecules in the solvent modify the N atoms at the 3-position of the benzimidazole molecules, with the help of hydroiodic acid, to form ionic liquids. The new perovskite materials do not contain alkali metal ions or organic ammonium ions, but rather ionic liquid cations (1,3-diethylbenzolamazole)⁺ and (1-methyl-3-ethylbenzimidazole)⁺, thus giving them excellent moisturizing properties. The study also improves the photocatalytic performance of these materials by making them into micron-sized sheets using the anti-solvent method. Under visible light, the materials show high efficiency in reducing Cr(VI) (95.3 % and 92.3 % for the two materials) and producing hydrogen from HI splitting (2053.59 and 1957.76 μmol g⁻¹h⁻¹). This research not only develops a method for creating moisture-resistant perovskites with ionic liquids but also shows potential for using these materials in photocatalytic reactions in water.