催化学报

催化学报 ›› 2017, Vol. 38 ›› Issue (2): 321-329.DOI: 10.1016/S1872-2067(16)62573-1

• 论文 • 上一篇    下一篇

石榴状单质铋(Bi)球与g-C3N4复合材料表现出超强可见光氧化NO性能

李宇涵a, 吕康乐a,c, 何咏基a,b, 赵再望a, 黄宇b   

  1. a 香港教育大学科学与环境系, 香港;
    b 中国科学院地球环境研究所气溶胶化学与物理重点实验室, 陕西西安 710061;
    c 中南民族大学资源与环境学院, 湖北武汉 430074
  • 收稿日期:2016-08-29 修回日期:2016-10-05 出版日期:2017-02-18 发布日期:2017-03-14
  • 通讯作者: Kangle Lv,Tel:+86-27-67841369;Fax:+86-27-67843918;E-mail:lvkangle@mail.scuec.edu.cn;Wingkei Ho,Tel:+852-29488255;Fax:+852-29487726;E-mail:keithho@eduhk.hk
  • 基金资助:

    国家重点基础研究发展规划（2016YFA0203000），香港特别行政区政府研究资助局杰出青年学者计划（ECS 809813），香港教育大学裘槎中国访问学者计划（2015-2016），国家自然科学基金（51672312和21373275）以及教育部“新世纪优秀人才支持计划”（NCET-12-0668）.

Enhanced visible-light photo-oxidation of nitric oxide using bismuth-coupled graphitic carbon nitride composite heterostructures

Yuhan Lia, Kangle Lva,c, Wingkei Hoa,b, Zaiwang Zhaoa, Yu Huangb   

  1. a Department of Science and Environmental Studies, The Education University of Hong Kong, Tai Po, N. T., Hong Kong, China;
    b Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Shanxi, China;
    c Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan 430074, Hubei, China
  • Received:2016-08-29 Revised:2016-10-05 Online:2017-02-18 Published:2017-03-14
  • Contact: 10.1016/S1872-2067(16)62573-1
  • Supported by:

    This work was supported by the National Program on Key Basic Research Project (2016YFA0203000), the Early Career Scheme (ECS 809813) from the Research Grant Council, Hong Kong SAR Government, the Croucher Foundation Visitorship for PRC Scholars 2015/16 at The Education University of Hong Kong, the National Natural Science Foundation of China (51672312, 21373275), and the Program for New Century Excellent Talents in University (NCET-12-0668).

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摘要：

采用一种原位合成工艺制备了具有类石榴结构的金属铋（Bi）单质修饰的g-C3N4复合材料（Bi-CN），并用于可见光氧化NO反应中.金属Bi单质镶嵌在CN层间形成的复合物，由于金属Bi单质显著的表面等离子体共振（SPR）作用可将光吸收范围由紫外光延展至近红外，极大地提高了复合物的光吸收.此外，由于Bi单质存在于复合物界面可产生内建莫特-肖特基效应，从而加快光生载流子的分离与转移.由此，Bi-CN复合物光催化剂展现出超强的光催化去除NO性能.我们提出了类石榴结构的形成以及相应的Bi-CN复合物光催化活性的提高机理.这不仅为高效的金属铋单质改性的g-C3N4基光催化剂提供了一种新的设计方案，也对g-C3N4基光催化的机制理解提出了新的见解.
通过X射线衍射、红外光谱和X射线光电子能谱结果发现Bi是以金属单质的形式存在于Bi-CN复合物中，这得益于我们采用了二水合铋酸钠（NaBiO3·2H2O）作为铋前驱体，从而成功避免了氧化态铋的形成.Bi-CN复合物中金属铋单质的存在有诸多优点.首先，金属铋单质具有显著的表面SPR效应，它的引入可大大提高复合物的光吸收能力和太阳光利用率.有研究表明，直径为150-200 nm的铋球能够在紫外-可见漫反射图谱（UV-vis）在λ=500 nm处呈现出典型的SPR峰，但本样品在λ=200-800 nm区间内并未发现该SPR峰.由于铋单质的共振受限于其尺寸大小、颗粒形状和构造环境.本文中球形铋单质的直径约为1 μm，其可能发生共振效应的峰位置应超过800 nm，因此未发现相应的SPR峰.其次，金属铋单质分散在CN层表面上构建的肖特基垫垒能够高效地阻止光生电子与空穴的复合，促进了光生载流子的分离与转移，从而提高光氧化NO进程.再者，金属铋单质的介入成功构造了Bi-CN异质结，在可见光照射下NO氧化反应中，Bi-CN复合物活性显著高于CN（22.2%）、CN-EG（36.4%）和Bi（14.1%），其中以10% Bi-CN活性最佳，NO去除率到70.4%，远远超过K插层的g-C3N4、Ag掺杂的g-C3N4和氧化石墨烯修饰的g-C3N4.
当复合物中金属铋单质含量超过10%时，其活性明显下降.这是因为大量的金属铋单质积聚在Bi-CN复合物表面上而造成物理堵塞，妨碍了CN吸收可见光，从而降低了其可见光吸收能力；同时导致只会吸收更多的紫外光（λ<280 nm）而不是可见光，因而其可见光催化氧化NO能力下降.

关键词: 金属铋, 表面等离子体共振, 光氧化, 一氧化氮, 可见光, 石墨型碳化氮

Abstract:

Pure bismuth (Bi) metal-modified graphitic carbon nitride (g-C3N4) composites (Bi-CN) with a pomegranate-like structure were prepared by an in situ method. The Bi-CN composites were used as photocatalysts for the oxidation of nitric oxide (NO) under visible-light irradiation. The inclusion of pure Bi metal in the g-C3N4 layers markedly improved the light absorption of the Bi-CN composites from the ultraviolet to the near-infrared region because of the typical surface plasmon resonance of Bi metal. The separation and transfer of photogenerated charge carriers were greatly accelerated by the presence of built-in Mott-Schottky effects at the interface between Bi metal and g-C3N4. As a result, the Bi-CN composite photocatalysts exhibited considerably enhanced efficiency in the photocatalytic removal of NO compared with that of Bi metal or g-C3N4 alone. The pomegranate-like structure of the Bi-CN composites and an explanation for their improved photocatalytic activity were proposed. This work not only provides a design for highly efficient g-C3N4-based photocatalysts through modification with Bi metal, but also offers new insights into the mechanistic understanding of g-C3N4-based photocatalysis.

Key words: Bismuth, Surface plasmon resonance, Photo-oxidation, Nitric oxide, Visible light, Graphitic carbon nitride