Fast preparation of oxygen vacancy-rich 2D/2D bismuth oxyhalides-reduced graphene oxide composite with improved visible-light photocatalytic properties by solvent-free grinding

Bismuth oxyhalides (BiOX, X = Cl, Br, I) exhibit excellent photocatalytic activity owing to their distinctive layered structures and suitable bandgaps. However, BiOX and its derived composites are usually fabricated via the liquid-phase strategy, which always produces waste liquid, thereby polluting the environment. Recently, BiOX/reduced graphene oxide (RGO) with two-dimensional/two-dimensional (2D/2D) heterostructures have been successfully prepared without using any solvent by one-pot mixing/grinding using chemicals such as bismuth nitrate pentahydrate, potassium halide, graphene oxide (GO), and BH4K. The fabricated BiOX/RGO heterostructures were endowed with oxygen-rich vacancies and a very short fabrication time of 15 min. During the synthesis process, BiOX can grow in situ on the GO due to Bi3+ ions; thus, BiOX could be adsorbed easily on the GO surface, with the negatively charged oxygen-containing functional group. Significantly, BH4K not only reduces GO to RGO but also introduces a suitable concentration of oxygen vacancies (OVs) in BiOX, which can photo-induce the carrier separation efficiency and effectively improve visible-light absorption. BiOX/RGO with a 2D/2D heterojunction structure provided a higher specific surface area and a larger heterogeneous interface and transferred photogenerated electrons regularly. Owing to the dual synergistic effects of the aforementioned features, BiOX/RGO can produce more active substances (h+, •OH, and •O2−) for the photodegradation of organic pollutants. The results showed that the photocatalytic performance of BiOCl/RGO, BiOBr/RGO, and BiOI/RGO was significantly improved as the degradation rate of Rhodamine B (RhB) under visible-light irradiation was 6, 3, and 2 times higher than that of pure BiOCl, BiOBr, and BiOI, respectively. Furthermore, BiOX/RGO displayed a similar enhanced photocatalytic effect on tetracycline degradation. Therefore, this work provides a versatile, green, and fast method to synthesize BiOX/RGO composites for the photodegradation of different organic pollutants.