Synthesis of “walnut‐like” BiOCl/Br solid solution photocatalyst by electrostatic self‐assembly method

Abstract

Summary In this paper, under the control strategy of surface charge of BiOCl photocatalyst and the electrostatic adsorption of anions and cations in potassium bromide (KBr) and polyvinylpyrrolidone (PVP), the self‐assembly of “walnut‐like” BiOCl/Br solid solution nanophotocatalyst at a lower temperature water bath was proposed for the first time. X‐ray diffraction (XRD), Raman, scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), energy‐dispersive system (EDS), X‐ray photoelectron spectroscopy (XPS), Brunauer‐Emmett‐Teller (BET), UV‐Vis, photoluminescence spectroscopy (PL) and Mott‐Schottky curve, transient photocurrent densities, and electrochemical impedance spectroscopy (EIS) were used to analyze the properties of materials, including its morphology, element distribution and chemical states, specific surface area, electrochemical property, and photogenic charge transfer. Based on the degradation performance of RhB dye wastewater and phenol in visible and ultraviolet light, and the band structure of BiOCl/Br solid solution, the reason for the improved photocatalytic activity was deeply discussed, and the possible degradation mechanism was also put forward. The above results show that Br− can be inserted into the crystal lattice of BiOCl under the effect of electrostatic adsorption to form solid solution by the interaction between atomic orbitals, which not only reduces the bandgap width but also improves the separation and mobility of photogenic electrons and holes, causing the absorbed light to shift red to the visible region. In addition, when the nBr−/nCl− = 0.67, “walnut‐like” BiOCl/Br solid solution was formed, and this kind of special core‐shell structure not only can increase the specific surface area, increase the number of active sites, but also can make the light reflect and refract many times in the cavity and further increase the utilization rate of light energy, and then the best photocatalytic activity was achieved. This study provides an new method to enhance the photocatalytic performance of BiOCl and be conducive to the development of modern material science.

A Facile Synthesis of BiO(ClBr)0.5−x/2Ix Microsphere Assembly as High‐efficiency Visible‐light Driven Photocatalyst

“…As the pure BiOX and their solid solutions belong to the point group of D 4 h, they exhibit all three central symmetric modes of A 1g , B 1g , and E g . [15] The Raman spectrum of BiOCl shown in Figure 1b includes strong bands at 60, 153, 203 cm À 1 ascribed to external-A 1g , A 1g , and E g mode of BiÀ Cl bonds while the B 1g and E g mode of ploidy-like belt motion of oxygen atoms at 387 cm À 1 are feeble. The humb signals at 70 and 95 cm À 1 could be attributed to the first-order scattering A 1g and E g mode of Bi.…”

“…The bonding information of as‐prepared samples was clarified using Raman spectroscopy. As the pure BiOX and their solid solutions belong to the point group of D 4 h, they exhibit all three central symmetric modes of A 1g , B 1g , and E g [15] . The Raman spectrum of BiOCl shown in Figure 1b includes strong bands at 60, 153, 203 cm −1 ascribed to external‐A 1g , A 1g , and E g mode of Bi−Cl bonds while the B 1g and E g mode of ploidy‐like belt motion of oxygen atoms at 387 cm −1 are feeble.…”

“…This could result in the better separation of photoinduced excitons due to the difference in preferable crystal planes for migration between electrons and holes. [15] The bonding information of as-prepared samples was clarified using Raman spectroscopy. As the pure BiOX and their solid solutions belong to the point group of D 4 h, they exhibit all three central symmetric modes of A 1g , B 1g , and E g .…”

“…This peak's disappearance in high I‐content indicates that the (110) plane is the preferable orientation in the obtained solid solutions. This could result in the better separation of photo‐induced excitons due to the difference in preferable crystal planes for migration between electrons and holes [15] …”

“…Flower‐like form of these BiOX was also reported using surfactant‐assisted self‐assembly [14] . The low‐temperature water bath was applied to synthesize a “walnut‐like” solid solution of BiOCl/Br, which performed as an efficient photocatalyst for phenol degradation [15] . Meanwhile, the composite of BiOCl/BiOBr was prepared using microwave‐assisted co‐precipitation with higher photocatalytic performance than the hydrothermal route [16] .…”