Enhanced photoactivity and oxidizing ability simultaneously via internal electric field and valence band position by crystal structure of bismuth oxyiodide

Herein, the photoactivity and oxidizing ability of bismuth oxyiodide were enhanced simultaneously via crystal structure regulation. The internal electric field is enhanced via unit cell dipole with various crystal structures. The reduction of I in bismuth oxyiodide crystal increased dipole and crystal internal electric field, as a result promoting the photogenerated charge separation. This is also the intrinsic reason for the different photoactivity of bismuth oxyiodide with various crystal structures (BiOI, Bi4O5I2 and Bi5O7I). Irradiated below 420 nm, the photocatalytic activity of Bi5O7I is 4.65 times and 6.59 times greater than that of Bi4O5I2 and BiOI, respectively. Meanwhile, since the decreasing of valence band position for bismuth oxyiodide with the reduction of I, the oxidizing ability remarkably increase, resulting the mineralization ability significantly strengthened. The crystal structure regulation is a promising candidate for enhancing both photoactivity and oxidizing ability of photo-catalysts simultaneously.