Indirect Substitution Constructing Halogen-Vacancy BiOCl_1–xI_n Solid Solution with a Suitable Surface Structure for Enhanced Photoredox Performance

Abstract

Photocatalytic technology has made a series of breakthroughs in environmental remediation, but the degradation performance of persistent heavy metal ions and organic pollutants is not particularly excellent. In addition, the layered structure of bismuth oxyhalides (BiOX, X = I, Br, and Cl) has been a popular material for photodegradation and photoelectrochemistry. Accordingly, with a view to construct a suitable band structure and control the surface structure, it is necessary to develop a strategy to synthesize a BiOCl 1−x I n solid solution with halogen vacancies. In this study, halogen vacancies are in situ introduced into the BiOCl 1−x I n solid solution through constructing chemical bonds between the hydroxyl groups in glycerol and the I ions during the growth process. The band of the halogen-vacancy BiOCl 1−x I n solid solution is widened and active sites centered at halogen vacancies are formed in the direction favorable for the photocatalytic reaction, resulting in enhanced performance in the reduction of Cr(VI) and the oxidation of phenol. The results obtained can provide a new idea for the design of efficient photocatalysts by controlling the formation of halogen vacancies.

In Situ Construction of BiO(ClBr)(1–x)/2Ix–n Solid Solution with Appropriate Surface Iodine Vacancies for Synergistically Boosting Visible-Light Photo-Oxidation Capability

“…12,13 To be more detailed, the band gaps of BiOCl, BiOBr, and BiOI in turn are 3.2, 2.7, and 1.7 eV, respectively. 14 The information unveils that BiOCl hardly responds to visible light and that there is a high recombination rate of photogenerated carriers and a poor oxidation capacity for BiOBr and BiOI. 15 As a consequence, it is essential that BiOX is intensively modified to accommodate the criteria for practical applications.…”

“…Unfortunately, owing to a lack of anticipation and prevention of the negative effects of industrial development, industrial organic wastewater has led to a variety of environmental problems which threaten the survival of the natural world’s flora and fauna. − Hence, it is imperative to take actions to solve the issues of environmental pollution. Photocatalysis is deemed to be a novel and green technology that has been widely adopted for water splitting, − CO 2 reduction, , nitrogen fixation, and degradation of organic contaminants. , In recent years, a relatively promising V-VI-VII bismuth oxyhalide (BiOX, X = Cl, Br, and I) ternary oxide has been preferred by investigators in view of its unparalleled layered structure and superb photocatalytic activity. , To be more detailed, the band gaps of BiOCl, BiOBr, and BiOI in turn are 3.2, 2.7, and 1.7 eV, respectively . The information unveils that BiOCl hardly responds to visible light and that there is a high recombination rate of photogenerated carriers and a poor oxidation capacity for BiOBr and BiOI .…”

Improving the Surface Oxygen Vacancy Concentration of Bi2O4 through the Pretreatment of the NaBiO3·2H2O Precursor as a High-Performance Visible Light Photocatalyst

“…Defect engineering, including anion vacancies, cation vacancies, and heteroatom dopants, based on semiconductor materials has triggered extensive investigation in recent years, since it can tune the band structure, improve the charge carriers’ separation efficiency, and provide more active sites to adsorb reactants on the photocatalysts. − Among the various defects, surface OVs, as the most prevalent defects, play an important role in enhancing the catalytic performance of photocatalysts themselves without the aid of other components . On the one hand, the existence of surface OVs could extend the spectral response range, which may enhance the utilization efficiency of solar energy. , On the other hand, the surface OVs on the photocatalyst could serve as traps to capture photoinduced electrons to promote the separation of charge carriers.…”

Constructing BiOBr1–xIx–y with Abundant Surface Br Vacancies for Excellent Visible-Light Photodegradation Capability of High-Concentration Refractory Contaminants

“…In addition, the electrons in the conduction band are more likely to migrate to vacancy defects instead of recombining with the holes, resulting in an extension of the lifetimes of the photogenerated carriers . As a result, BiOBr 0.6 I 0.4– y possesses more electrons and holes involved in the surface redox reaction . Overall, Figure e concludes that the vacancy defects in BiOBr 0.6 I 0.4– y can serve as trap states, where the photogenerated electrons and holes are effectively separated and significantly increase their utilization efficiency for interfacial redox reactions, thus exhibiting a remarkable photodegradation capacity for high-concentration pollutants.…”

“…Considering the crucial contribution of the Br 4p state to the band structure of BiOBr, the existence of Br vacancies is able to directly reduce the band gap by modifying the position of the VBM of BiOBr 0.6 I 0.4– y . Although BiOBr 0.6 I 0.4 has the narrowest band gap, the VBM of BiOBr 0.6 I 0.4– y is greater than that of BiOBr 0.6 I 0.4 , which facilitates the generation of holes with strong oxidizing capacity . Comprehensively, BrVs-rich BiOBr 0.6 I 0.4– y possesses the advantage of improved visible-light absorption due to the narrow band gap as well as enhanced photooxidation ability due to the more positive VBM position.…”