催化学报 ›› 2020, Vol. 41 ›› Issue (1): 62-71.DOI: 10.1016/S1872-2067(19)63421-2

• 光催化产氢 • 上一篇    下一篇

碳纳米管@碳化硅同轴异质结纳米管非金属光催化剂产氢性能

周训富, 高琼芝, 杨思源, 方岳平   

  1. 华南农业大学材料与能源学院, 广东广州 510642
  • 收稿日期:2019-04-29 修回日期:2019-06-03 出版日期:2020-01-18 发布日期:2019-10-22
  • 通讯作者: 杨思源, 方岳平
  • 基金资助:
    国家自然科学基金(21673083,21802046);广东省科技项目(2017A030313090,2014A030310427).

Carbon nanotube@silicon carbide coaxial heterojunction nanotubes as metal-free photocatalysts for enhanced hydrogen evolution

Xunfu Zhou, Qiongzhi Gao, Siyuan Yang, Yueping Fang   

  1. College of Materials and Energy, South China Agricultural University, Guangzhou 510642, Guangdong, China
  • Received:2019-04-29 Revised:2019-06-03 Online:2020-01-18 Published:2019-10-22
  • Supported by:
    This research was supported by the National Natural Science Foundation of China (21673083, 21802046). The authors thank the Guangdong Provincial Science and Technology Project (2017A030313090, 2014A030310427).

摘要: 近年来,光催化裂解水产氢(H2)引起了广泛的关注.储量丰富,环境友好的非金属无机半导体β-SiC(立方相碳化硅)具有适当的带隙(Eg=2.4eV,ECB=-0.9V),是一种潜在的光催化剂.受限于SiC光催化剂内部光生电子-空穴对的快速复合,SiC光催化剂的效率较低.已有的关于SiC光催化剂改性的报道主要包括构建纳米SiC,构建SiC异质结,构建碳/SiC材料杂化材料.进一步的研究表明,SiC与碳材料之间通过紧密的界面接触形成了肖特基结,能将SiC表面的光生电子快速转移,抑制光生电子-空穴对的快速复合,从而提高光催化分解水产氢的活性.另一方面,碳纳米管(CNTs)具有良好的电子导电性,一维有序的管腔所形成的电子快速传导路径.因此,将半导体光催化剂与CNTs复合,是一种制备先进的光催化剂的有效策略.
本文利用Si蒸气与CNTs之间的气-固反应,在CNTs表面原位生长SiC纳米包覆层,成功地制备了一维同轴核-壳CNTs@SiC纳米管.高分辨率透射电子显微镜图像表明,SiC与CNTs之间是通过Si-C共价键原子接触,并得到X射线光电子能谱的证实.将一部分CNTs@SiC纳米管在空气中750oC煅烧2h以除去CNTs,得到纯SiC纳米颗粒作为对比组.紫外-可见吸收光谱表明,CNTs能够促进SiC对光的吸收.荧光发射光谱(PL),瞬态荧光寿命测试,瞬态光电流测试以及交流阻抗(EIS)测试表明,CNTs能够促进SiC表面光生电子的传输与分离,有利于提升光催化效率.以0.1mol/L Na2S溶液作为牺牲剂,在模拟太阳光(A.M 1.5)照射下,CNTs@SiC纳米管(不额外负载Pt等贵金属作为助剂)的产氢速率为118.5μmol g-1 h-1,是纯SiC纳米颗粒(21.1μmol g-1h-1)的5.62倍.经过20h的光照测试,CNTs@SiC纳米管的光催化性能无明显衰减;X射线衍射测试与扫描电子显微镜图像表明,CNTs@SiC纳米管的结构与形貌反应前后几乎无变化.莫特-肖特基测试表明,CNTs的费米能级比SiC低,因此SiC表面的光生电子能够快速地转移到CNTs,并且CNTs的良好导电性与一维有序的管腔所形成的长的电子传导路径能够进一步地增加电子寿命,促进光生电子参与光催化反应.另外,通过原子连接的同轴核-壳CNTs@SiC纳米管提供了大量且有效的电子传输路径.因此,与纯SiC纳米晶等同类材料相比,无机非金属CNTs@SiC纳米管具有更强的光催化氢活性.

关键词: 碳化硅, 同轴核-壳纳米管, 纳米异质结, 电荷分离, 析氢

Abstract: Considerable research efforts have been devoted to developing novel photocatalysts with increased performances by hybridizing inorganic nanomaterials with carbon nanotubes. In this work, one-dimensional coaxial core-shell carbon nanotubes@SiC nanotubes were successfully synthesized via in situ growth of SiC coatings on carbon nanotubes by a vapor-solid reaction between silicon vapor and carbon nanotubes. High-resolution transmission electron microscope images show that SiC and carbon nanotubes link to form a robust heterojunction with intrinsic atomic contact, which results in efficient separation of the photogenerated electron-hole pairs on SiC and electron transfer from SiC to carbon nanotubes. Compared with those of similar materials such as pure SiC nanocrystals and SiC nanotubes, the metal-free carbon nanotubes@SiC exhibits an enhanced photocatalytic activity for hydrogen evolution, which is attributed to the enhanced light absorption and the efficient interfacial charge transfer/separation brought about by their one-dimensional coaxial nanoheterostructures. Moreover, the photocatalytic stability of the metal-free carbon nanotubes@SiC was tested for over 20 h without any obvious decay.

Key words: Silicon carbide, Coaxial core-shell nanotubes, Nanoheterostructures, Charge separation, Hydrogen evolution