Understanding the composition and electronic structure dependent photocatalytic performance of bismuth oxyiodides

Abstract

A series of bismuth oxyiodides were obtained by calcining the precursor compound (Bi₇O₉I₃). Their compositions and electronic structures were analyzed by various physicochemical characterizations, slurry method measurements and theoretical calculations. Iodine vacancies appearing at elevated temperatures before the phase transition contribute to the increased photocatalytic activity, which can be attributed to the increase of band gaps, downward shifts of band potentials and the change of semiconductor behavior from p type to n type. The catalyst obtained at 400 °C displayed an excellent photocatalytic performance for phenol degradation, and it was characterized as a composite of two components with well-matched band potentials and good contact interfaces. Photogenerated holes were revealed as the main active species in the phenol degradation. This study could bring insights into the fabrication of novel highly efficient bismuth oxyiodide composites by simultaneously controlling the extent of phase transition and the amount of iodine vacancies.