Improved photocatalytic activity of few-layer Bi4O5I2 nanosheets induced by efficient charge separation and lower valence position

Abstract

Ultrasmall few-layer Bi4O5I2 nanosheets were controlled prepared via an ionic liquid [Hmim]I (1-hexyl-3-methylimidazolium iodide)-mannitol assisted solvothermal method accompanied by adjusting to the proper pH. Multiple characterizations were employed to investigate the composition, structure, morphology, optical absorption property and photocatalytic performance of the ultrasmall few-layer Bi4O5I2 nanosheets materials. During the synthesis process, ionic liquid acted as solvent, capping agent and provided the I source to form the Bi4O5I2 nanostructure, resulting in the thinnest Bi4O5I2 materials (about 6 layers) reported up to now. DLS analysis indicated the Bi4O5I2 diameter was mainly distributed in the range of 37–52 nm. Organic dye rhodamine B (RhB) and colourless ciprofloxacin (CIP) were used as target pollutants to estimate the photocatalytic performance of as-prepared Bi4O5I2 nanosheets. PL analysis showed that Bi4O5I2 owned the lower recombination rate of the photogenerated charge carriers. The improved photocatalytic activity of Bi4O5I2 nanosheets was attributed to the ultrasmall few-layer structure and varied energy band structure which favored the efficient separation of electron-hole pairs and the lower valence position of Bi4O5I2 greatly increased the oxidizing ability. Different from the active species of BiOI, the photogenerated holes and ·OH were determined to be the main active species of Bi4O5I2 during the photodegradation process.