Theoretical study of the influence of halogen vacancies on the properties of bismuth oxyiodide

Abstract

Bismuth oxyhalides (BiOX, X: halide) are an efficient group of photocatalysts that achieve the degradation of organic pollutants in water and also possess bactericidal properties. In particular, bismuth oxyiodide BiOI can be activated under solar radiation due to its smaller band gap (Eg). Experimentally, different structures and vacancy concentrations can be obtained by varying the synthesis procedure, allowing for tuning of the band gap. In this work, we present results obtained from calculations using the commercial VASP package based on Density Functional Theory and including Van der Waals forces. The modeled systems Bi₇O₉I₃, Bi₄O₅I₂, and Bi₅O₇I correspond to those reported experimentally. We can conclude that a decrease in iodine concentration results in increased band gaps and shifts to shorter wavelengths. In summary, the impact of iodine concentration changes is directly reflected in the optoelectronic properties of these systems.