Ultransonic-assisted alcoholysis preparation of BiOClxBr1−x modified BiOF microstructure with enhanced photocatalytic performance

Abstract

A series of BiOF/BiOCl x Br 1−x composites with different BiOF contents have been synthesized by means of ultrasonicassisted alcoholysis for the first time. The as-prepared samples were characterized by such methods as XRD, SEM, TEM, EDS, Mapping, BET, UV-Vis, XPS and PL spectra. The photocatalytic activity of samples under visible-light irradiation was evaluated by the degradation of Rhodamine. The results revealed that BiOF/BiOCl 0.75 Br 0.25 composite exhibited much higher photocatalytic activity than pure BiOF and BiOCl 0.75 Br 0.25 . And the 30%BiOF/BiOCl 0.75 Br 0.25 composite displayed the highest photocatalytic performance, reaching up 97% after irradiating with visible light for 45 min. The improvement of photocatalytic activity could be ascribed to the increased visible light absorption, its larger specific surface area and the enhanced electron-hole pairs effective separation. Moreover, the•O 2 − and h + were considered as the main active species during photocatalytic process. At last, the possible mechanism of the photocatalytic property was proposed in this paper.

Fast Scalable Synthetic Methodology to Prepare Nanoflower‐Shaped Bi/BiOClxBr1−x Heterojunction for Efficient Immobilized Photocatalytic Reactors under Visible Light Irradiation

“…As for the high‐resolution XPS spectra of the Cl 2p (Figure 4e), two main peaks at 196.5 and 198.4 eV appeared in the as‐prepared Bi/BiOCl x Br 1− x films (except at x = 0, BiOBr), which are attributed to Cl 2p 3/2 and Cl 2p 1/2 , respectively. [ 42 ] Meanwhile, the intensity of these peaks was found to increase with the increase in the chlorine ratio in the as‐prepared Bi/BiOCl x Br 1− x films. In addition, there was another peak that appeared in the XPS Cl 2p spectrum of BiOCl which is usually ascribed to chemical bonds between chlorine and organic species.…”

“…The corresponding bandgap energy of the as‐prepared Bi/BiOCl x Br 1− x films was estimated from the plots of ( αhv ) n /2 versus hv (Figure 5b) to be 2.5, 2.6, 2.7, 2.9, and 3.2 eV for Bi/BiOBr, Bi/BiOCl 0.2 Br 0.8 , Bi/BiOCl 0.5 Br 0.5 , Bi/BiOCl 0.8 Br 0.2 , and Bi/BiOCl, respectively. [ 42 ] The bandgap energy was gradually decreased with the increase of the Br:Cl molar ratio indicating the modulation of their band structure upon changing the molar ratio. Previous studies [ 42,44 ] reported that there is no change in the positions of the conduction band (CB) bottom upon increasing od Br content, whereas those of valence band (VB) top gradually uplift providing the higher absorption intensity of the visible‐light irradiation upon the increasing of Br content in the solid solution.…”

“…[ 42 ] The bandgap energy was gradually decreased with the increase of the Br:Cl molar ratio indicating the modulation of their band structure upon changing the molar ratio. Previous studies [ 42,44 ] reported that there is no change in the positions of the conduction band (CB) bottom upon increasing od Br content, whereas those of valence band (VB) top gradually uplift providing the higher absorption intensity of the visible‐light irradiation upon the increasing of Br content in the solid solution.…”

“…The absorption spectrum of RhB (300–750 nm) was used to estimate its concentration at 10‐min time intervals. The photodegradation rate (%) was estimated based on the following equation: [ 42 ] Photodegradation rate (%) = (1 − C t ∕ C 0 ) × 100%, where C 0 and C t are concentrations of RhB at 0 and t min, respectively.…”

“…Generally, high-frequency ultrasound irradiation (i.e., ultrasonication probe) has been proven to be one of the most effective environmentally friendly techniques to prepare nanostructured photocatalytic materials in stable colloidal dispersion form (i.e., unagglomerated suspended particles) as a result of the homogenous mixing of the reactants and significant reduction of the aggregation of the products. [40,41] A few studies reported the use of high-frequency ultrasound irradiation alone as an assisted method for the preparation of BiOXs and their solid solutions, which is incorporated with other steps such as stirring for a long time [42] or high-temperature thermal treatment. [43] Notably, the use of LFUI (i.e., typical ultrasonication bath) to prepare BiOXs and their solid solutions as a single-step strategy has not been reported yet.…”