物理化学学报 >> 2021, Vol. 37 >> Issue (6): 2008047.doi: 10.3866/PKU.WHXB202008047

所属专题: 先进光催化剂设计与制备

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羧基功能化石墨烯增强TiO2光催化产氢性能

王苹1,*(), 李海涛1, 曹艳洁1, 余火根1,2,*()   

  1. 1 武汉理工大学化学化工与生命科学学院,武汉 430070
    2 武汉理工大学硅酸盐建筑材料国家重点实验室,武汉 430070
  • 收稿日期:2020-08-17 录用日期:2020-09-22 发布日期:2020-09-28
  • 通讯作者: 王苹,余火根 E-mail:wangping0904@whut.edu.cn;yuhuogen@whut.edu.cn
  • 基金资助:
    国家自然科学基金(21771142);国家自然科学基金(51872221);中央高校基本科研业务费(WUT2019IB002)

Carboxyl-Functionalized Graphene for Highly Efficient H2-Evolution Activity of TiO2 Photocatalyst

Ping Wang1,*(), Haitao Li1, Yanjie Cao1, Huogen Yu1,2,*()   

  1. 1 School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
    2 State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China
  • Received:2020-08-17 Accepted:2020-09-22 Published:2020-09-28
  • Contact: Ping Wang,Huogen Yu E-mail:wangping0904@whut.edu.cn;yuhuogen@whut.edu.cn
  • About author:Huogen Yu, Emails: yuhuogen@whut.edu.cn (H.Y.)
    Ping Wang, Emails: wangping0904@whut.edu.cn (P.W.); Tel.: +86-27-87756779-8303 (P.W.)
  • Supported by:
    the National Natural Science Foundation of China(21771142);the National Natural Science Foundation of China(51872221);the Fundamental Research Funds for the Central Universities, China(WUT2019IB002)

摘要:

利用半导体光催化剂(CdS、g-C3N4、TiO2等)产氢是将太阳能转换为氢能以满足未来能源需求的前瞻性策略之一。在众多光催化剂中,TiO2因其合适的还原电位和出色的化学稳定性而备受关注。然而,TiO2受光激发产生的电子和空穴容易发生猝灭而表现出有限的光催化性能。由于具备优异的导电性和稳定性,石墨烯可以作为一种有效的电子助剂加速光生电子的传输,进而提高TiO2的产氢性能。但是,在光催化反应中,除了光生电子的快速转移外,石墨烯表面的界面产氢反应也非常重要。因此,有必要进一步优化石墨烯的微观结构(功能化石墨烯),以提高石墨烯基TiO2光催化剂的产氢性能。通常,石墨烯的功能化是一个可以在石墨烯表面上引入产氢活性位点的有效策略。与非共价功能化(例如在石墨烯表面上加载Pt,MoSx和CoSx)相比,石墨烯的共价功能化可以通过化学反应将产氢活性位点与石墨烯表面的官能团相结合,并形成强相互作用,有利于界面的产氢反应。本文将开环和酯化反应制备的羧基功能化石墨烯(rGO-COOH)成功地通过超声辅助自组装法修饰TiO2得到高活性的TiO2/rGO-COOH光催化剂。傅立叶变换红外(FTIR)光谱显著增强的―COOH官能团特征峰、X射线光电子能谱(XPS)中的峰面积变化和热重(TG)曲线的质量变化证实了GO向rGO-COOH的成功转变。X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、XPS和紫外可见漫反射光谱(UV-Vis)等一系列表征可证明TiO2/rGO-COOH光催化剂的成功合成。光催化产氢测试结果表明TiO2/rGO-COOH样品表现出较高的产氢活性(254.2 μmol·h-1·g-1),分别是TiO2/GO和TiO2的2.06和4.48倍。光催化活性提高可归因于羧基功能化石墨烯中具有优异亲核性的羧基可以富集氢离子,并作为有效的产氢活性位点,显著地提高TiO2的界面产氢反应速率。这项研究为我们在光催化产氢领域中开发高活性石墨烯负载的光催化剂提供了新的思路。

关键词: 羧基功能化石墨烯, 羧基基团, TiO2, 光催化产氢

Abstract:

The use of semiconductor photocatalysts (CdS, g-C3N4, TiO2, etc.) to generate hydrogen (H2) is a prospective strategy that can convert solar energy into hydrogen energy, thereby meeting future energy demands. Among the numerous photocatalysts, TiO2 has attracted significant attention because of its suitable reduction potential and excellent chemical stability. However, the photoexcited electrons and holes of TiO2 are easily quenched, leading to limited photocatalytic performance. Furthermore, graphene has been used as an effective electron cocatalyst in the accelerated transport of photoinduced electrons to enhance the H2-production performance of TiO2, owing to its excellent conductivity and high charge carrier mobility. For an efficient graphene-based photocatalyst, the rapid transfer of photogenerated electrons is extremely important along with an effectual interfacial H2-production reaction on the graphene surface. Therefore, it is necessary to further optimize the graphene microstructures (functionalized graphene) to improve the H2-production performance of graphene-based TiO2 photocatalysts. The introduction of H2-evolution active sites onto the graphene surface is an effective strategy for the functionalization of graphene. Compared with the noncovalent functionalization of graphene (such as loading Pt, MoSx, and CoSx on the graphene surface), its covalent functionalization can provide a strong interaction between graphene and organic molecules in the form of H2-evolution active sites that are produced by chemical reactions. In this study, carboxyl-functionalized graphene (rGO-COOH) was successfully modified via ring-opening and esterification reactions on the TiO2 surface by using an ultrasound-assisted self-assembly method to prepare a high-activity TiO2/rGO-COOH photocatalyst. The Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and thermogravimetric (TG) curves revealed the successful covalent functionalization of GO to rGO-COOH by significantly enhanced ―COOH groups in FTIR and increased peak area of carboxyl groups in XPS. A series of characterizations, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), XPS, and UV-Vis adsorption spectra, were performed to demonstrate the successful synthesis of TiO2/rGO-COOH photocatalysts. The experimental data for the hydrogen-evolution rate showed that the TiO2/rGO-COOH displayed an extremely high hydrogen-generation activity (254.2 μmol∙h−1∙g−1), which was 2.06- and 4.48-fold higher than those of TiO2/GO and TiO2, respectively. The enhanced photocatalytic activity of TiO2/rGO-COOH is ascribed to the carboxyl groups of carboxyl-functionalized graphene, which act as effective hydrogen-generation active sites and enrich hydrogen ions owing to their excellent nucleophilicity that facilitates the interfacial hydrogen production reaction of TiO2. This study provides novel insights into the development of high-activity graphene-supported photocatalysts in the hydrogen-generation field.

Key words: Carboxyl-functionalized graphene, Carboxyl groups, TiO2, Photocatalytic H2 evolution

MSC2000: 

  • O643