催化学报 ›› 2017, Vol. 38 ›› Issue (12): 2030-2038.DOI: 10.1016/S1872-2067(17)62941-3

• 论文 • 上一篇    下一篇

Bi12O17Br2和Bi4O5Br2纳米片的简易制备及光催化氧化NO机理的原位漫反射红外光谱研究

张文东a,b, 刘晓莉a, 董兴安c, 董帆c, 张育新a   

  1. a 重庆大学材料科学与工程学院, 重庆 400044;
    b 重庆师范大学科研处, 重庆 401331;
    c 重庆工商大学环境与资源学院, 重庆市催化与功能有机分子重点实验室, 重庆 400067
  • 收稿日期:2017-09-23 修回日期:2017-10-26 出版日期:2017-12-18 发布日期:2017-12-29
  • 通讯作者: 董帆, 张育新
  • 基金资助:

    国家自然科学基金(51708078,21576034);重庆市博士后科学基金(Xm2016027);重庆市高校创新团队(CXTDG201602014,CXTDX201601016).

Facile synthesis of Bi12O17Br2 and Bi4O5Br2 nanosheets: In situ DRIFTS investigation of photocatalytic NO oxidation conversion pathway

Wendong Zhanga,b, Xiaoli Liua, Xing'an Dongc, Fan Dongc, Yuxin Zhanga   

  1. a College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
    b Department of Scientific Research Management, Chongqing Normal University, Chongqing 401331, China;
    c Chongqing Key Laboratory of Catalysis and Functional Organic Molecules, College of Environment and Resources, Chongqing Technology and Business University, Chongqing 400067, China
  • Received:2017-09-23 Revised:2017-10-26 Online:2017-12-18 Published:2017-12-29
  • Supported by:

    This work is supported by the National Natural Science Foundation of China (51708078, 21576034), Chongqing Postdoctoral Science Foundation funded project (Xm2016027), the Innovative Research Team of Chongqing (CXTDG201602014, CXTDX201601016).

摘要:

BiOBr因具有合适的能带结构和独特的层状纳米结构而广泛应用于可见光催化领域,但其低的可见光利用率和高的光生电子-空穴对复合率,限制了其实际应用.最近,非整比BiOBr纳米材料表现出了良好的可见光催化性能.本课题组分别采用简易水热法和常温法制备得Bi12O17Br2和Bi4O5Br2纳米片,并表现出良好的可见光催化性能.然而,对于Bi12O17Br2和Bi4O5Br2的可见光催化氧化NO的转化路径及反应机理还不清楚.基于此,本文采用射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、电子自旋共振(ESR)、电子顺磁共振(EPR)和比表面积-孔结构(BET-BJH)等手段研究了Bi12O17Br2和Bi4O5Br2的理化性能,通过原位红外光谱(in situ DRIFTS)研究了Bi12O17Br2和Bi4O5Br2的可见光催化氧化NO的转化路径及反应机理.
XRD结果表明,在常温碱性环境下,OH-离子逐步取代BiOBr中的Br-离子制备得单斜晶相Bi4O5Br2;在水热碱性环境下,OH-离子进一步取代Bi4O5Br2中的Br-离子制备得四方晶相Bi12O17Br2.SEM和TEM结果表明,Bi12O17Br2是由不规则纳米片堆叠形成的紧密且厚实的层状结构,Bi4O5Br2是由纳米片和纳米颗粒无序堆积形成的多孔疏松结构.BET-BJH测试结果显示,Bi4O5Br2的比表面积和孔容(37.2 m2/g,0.215 cm3/g)显著高于Bi12O17Br2(8.7 m2/g,0.04 cm3/g).UV-Vis DRS测试结果显示,Bi12O17Br2和Bi4O5Br2均显示了良好的可见光吸收能力.可见光催化去除NO的测试结果表明,Bi4O5Br2(41.8%)的光催化活性明显高于Bi12O17Br2(28.3%).并且,在5次可见光催化循环实验后,Bi4O5Br2(41.1%)表现出良好可见光催化稳定性.ESR测试结果表明,Bi12O17Br2和Bi4O5Br2参与反应的主要活性物种均为·OH自由基,Bi4O5Br2产生·OH自由基明显强于Bi12O17Br2.EPR测试结果表明,Bi4O5Br2的氧空位明显多于Bi12O17Br2,丰富的氧空位更有利于NO的有效吸附.由此可见,Bi12O17Br2和Bi4O5Br2表现出不同的理化特性.
可见光催化氧化NO的原位红外光谱表明,只在Bi12O17Br2光催化氧化NO的转化路径中会生成中间产物N2O3,表明Bi12O17Br2和Bi4O5Br2具有不同的NO光催化转化路径.结合上述表征结果认为,Bi4O5Br2比Bi12O17Br2表现出更优异可见光催化性能的主要原因有以下四个方面为:(1)Bi4O5Br2拥有更高的比表面积和更大的孔容,有利于NO的吸附、反应中间产物的转移和提供更多的活性位点参与光催化反应;(2)Bi4O5Br2可以生成更多的·OH自由基和拥有更强的价带空穴氧化能力;(3)NO中的O原子可以与Bi4O5Br2的氧空位结合,从而提供更多的反应位点;(4)Bi4O5Br2的光催化反应中可以生成中间产物N2O3,可以降低NO转化成NO3-的反应活化能.

关键词: Bi12O17Br2, Bi4O5Br2, 原位漫反射红外光谱研究, 转化路径, NO氧化

Abstract:

Bi12O17Br2 and Bi4O5Br2 visible-light driven photocatalysts, were respectively fabricated by hydrothermal and room-temperature deposition methods with the use of BiBr3 and NaOH as precursors. Both Bi12O17Br2 and Bi4O5Br2 were composed of irregular nanosheets. The Bi4O5Br2 nanosheets exhibited high and stable visible-light photocatalytic efficiency for ppb-level NO removal. The performance of Bi4O5Br2 was markedly higher than that of the Bi12O17Br2 nanosheets. The hydroxyl radical (·OH) was determined to be the main reactive oxygen species for the photo-degradation processes of both Bi12O17Br2 and Bi4O5Br2. However, in situ diffuse reflectance infrared Fourier transform spectroscopy analysis revealed that Bi12O17Br2 and Bi4O5Br2 featured different conversion pathways for visible light driven photocatalytic NO oxidation. The excellent photocatalytic activity of Bi4O5Br2 resulted from a high surface area and large pore volumes, which facilitated the transport of reactants and intermediate products, and provided more active sites for photochemical reaction. Furthermore, the Bi4O5Br2 nanosheets produced more ·OH and presented stronger valence band hole oxidation. In addition, the oxygen atoms of NO could insert into oxygen-vacancies of Bi4O5Br2, which provided more active sites for the reaction. This work gives insight into the photocatalytic pollutant-degradation mechanism of bismuth oxyhalide.

Key words: Bi12O17Br2, Bi4O5Br2, In situ diffuse reflectance infrared Fourier transform spectroscopy investigation, Conversion pathway, NO oxidation