Oxygen defects-induced charge transfer in Bi7O9I3 for enhancing oxygen activation and visible-light degradation of BPA.

Two-dimensional (2D) bismuth-based semiconductors have aroused intensive concern owing to their prominent photocatalytic activity for organic pollutants removal. In this work, a facile strategy for introducing oxygen vacancy in Bi-based oxyiodides (BixOyIz) sheet-like architectures to activate molecular oxygen was proposed. The structure, photoelectric properties and visible light (λ > 420 nm) induced photocatalytic activities of these samples for decomposition of bisphenol A (BPA) were systematically characterized and evaluated. The as-prepared Bi7O9I3 with a feeding Bi/I molar ratio of 1:1 exhibited the best photocatalytic activity comparable to those of similarly synthesized Bi7O9I3 with other molar ratios and BiOIO3 catalysts. The optimal Bi7O9I3 achieved excellent photocatalytic activity with 99.6 % degradation efficiency of BPA within 20 min and superior structural stability with 95.1 % degradation retention over 5 cycling tests. In addition, the resulting Bi7O9I3 sample displayed a high mineralization efficiency of BPA. Importantly, the plenty of oxygen vacancies (Vos) exsiting in Bi7O9I3 played the dominant role in both accelerating electron transfer and activating molecular oxygen to facilitate the generation of superoxide radical (O2·-) and singlet oxygen (1O2), thereby proceeding oxidative degradation of BPA molecules during photoreactions. The efforts and attempts are also extendable to synthesis other 2D photocatalysts, providing potential for effective charge-carrier separation and molecular oxygen activation.