Controllable design of bismuth oxyiodides by in-situ self-template phase transformation and heterostructure construction for photocatalytic removal of gas-phase mercury

In this work, various bismuth oxyiodides were prepared by in-situ phase transformation and heterostructure construction through a simple calcination method with BiOI as self-sacrificial template, including BiOI/Bi4O5I2 heterojunction, Bi4O5I2, Bi4O5I2/Bi5O7I heterojunction and Bi5O7I. The physicochemical properties of the samples synthesized at different calcination temperatures were analyzed through a series of characterizations. The photocatalytic activity was investigated by photocatalytic removal of gas-phase Hg0. The results indicate that they exhibit different photocatalytic properties in the order of Bi4O5I2/Bi5O7I > BiOI/Bi4O5I2 > Bi4O5I2 > Bi5O7I > BiOI, which is related to their visible light absorption, specific surface area, energy band structure and charge separation efficiency. In addition, the reasonable charge migration mechanism and the photocatalytic reaction mechanism for gas-phase Hg0 removal were proposed.