Abstract
Surface defect of nanomaterials is an important physical parameter which significantly influences their physical and chemical performances. In this work, high concentration of surface oxygen vancancies (SOVs) are successfully introduced on {001} facets exposed BiOBr nanosheets via a simple surface modification using polybasic carboxylic acids. The chelation interaction between carboxylic acid anions and Bi3+ results in the weakness of Bi-O bond of BiOBr. Afterwards, under visible-light irradiation, the oxygen atoms would absorb the photo-energy and then be released from the surface of BiOBr, leaving SOVs. The electron spin resonance (ESR), high-resolution transmission electron microscopy (HRTEM), and UV–vis diffuse reflectance spectra (DRS) measurements confirm the existence of SOVs. The SOVs can enhance the absorption in visible light region and improve the separation efficiency of photo-generated charges. Hence, the transformation rate of adsorbed O2 on the as-prepared BiOBr with SOVs to superoxide anion radicals (•O2−) and the photocatalytic activity are greatly enhanced. Based on the modification by several carboxylic acids and the photocatalytic results, we propose that carboxylic acids with natural bond orbital (NBO) electrostatic charges absolute values greater than 0.830 are effective in modifying BiOBr.
Highlights
In recent years, two-dimensional layer-structured inorganic photocatalysts such as carbon-containing compounds, transition metal oxides and transition metal dichalcogenides, have received massive research interest due to their unique structures and promising properties[21,22,23,24,25,26]
In-situ fabrication of surface oxygen vacancies (SOVs) was realized via a hydrothermal strategy followed by irradiation treatment with oxalic acid as the modifier
The covalent binding between Bi and O, and their highly dense arrangement in [Bi2O2] layers would strongly inhibit the diffusion of dopant precursor, resulting in a surface oxalic acid anions doping
Summary
Xiao-jing Wang[1], Ying Zhao[2], Fa-tang Li1, Li-jun Dou[1], Yu-pei Li1, Jun Zhao1 & Ying-juan Hao[1]. The chelation interaction between carboxylic acid anions and Bi3+ results in the weakness of Bi-O bond of BiOBr. Afterwards, under visible-light irradiation, the oxygen atoms would absorb the photo-energy and be released from the surface of BiOBr, leaving SOVs. The electron spin resonance (ESR), high-resolution transmission electron microscopy (HRTEM), and UV–vis diffuse reflectance spectra (DRS) measurements confirm the existence of SOVs. The SOVs can enhance the absorption in visible light region and improve the separation efficiency of photogenerated charges. It is known that polybasic carboxylic acids have strong chelation ability; we employ several polybasic carboxylic acids for coordination with Bi ions on the surface of BiOBr. As a result, the bond strength of Bi-O is weakened, leading to the removal of O atoms under visible light illumination and the formation of SOVs. After the introduction and confinement of SOVs in {001} facet-dominated BiOBr nanosheets, the photocatalytic activity and transformation rate of adsorbed O2 reduced to O2− radicals are significantly improved
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