物理化学学报 >> 2021, Vol. 37 >> Issue (6): 2010027.doi: 10.3866/PKU.WHXB202010027

所属专题: 先进光催化剂设计与制备

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理论计算研究二维/二维BP/g-C3N4异质结的光催化CO2还原性能

费新刚1, 谭海燕2,*(), 程蓓1, 朱必成1,*(), 张留洋1,*()   

  1. 1 武汉理工大学,材料复合新技术国家重点实验室,武汉 430070
    2 湖北民族大学,化学与环境工程学院,湖北 恩施 445000
  • 收稿日期:2020-10-13 录用日期:2020-11-04 发布日期:2020-11-12
  • 通讯作者: 谭海燕,朱必成,张留洋 E-mail:Jftanhaiyan@sina.com;zhubicheng1991@whut.edu.cn;zly2017@whut.edu.cn
  • 基金资助:
    国家重点研发计划(2018YFB1502001);国家自然科学基金(51872220);国家自然科学基金(21905219);国家自然科学基金(51932007);国家自然科学基金(U1905215);国家自然科学基金(21871217);国家自然科学基金(U1705251);博士后创新人才支持计划(BX20180231);中国博士后科学基金(2020M672432);湖北省博士后创新研究岗位项目

2D/2D Black Phosphorus/g-C3N4 S-Scheme Heterojunction Photocatalysts for CO2 Reduction Investigated using DFT Calculations

Xingang Fei1, Haiyan Tan2,*(), Bei Cheng1, Bicheng Zhu1,*(), Liuyang Zhang1,*()   

  1. 1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China
    2 School of Chemistry and Environmental Engineering, Hubei University for Nationalities, Enshi 445000, Hubei Province, China
  • Received:2020-10-13 Accepted:2020-11-04 Published:2020-11-12
  • Contact: Haiyan Tan,Bicheng Zhu,Liuyang Zhang E-mail:Jftanhaiyan@sina.com;zhubicheng1991@whut.edu.cn;zly2017@whut.edu.cn
  • About author:Email: zly2017@whut.edu.cn; Tel.: +86-15717179660 (L.Z.)
    Email: zhubicheng1991@whut.edu.cn; Tel.: +86-13296512925 (B.Z.)
    Email: Jftanhaiyan@sina.com; Tel.: +86-15172953185 (H.T.)
  • Supported by:
    the National Key Research and Development Program of China(2018YFB1502001);the National Natural Science Foundation of China(51872220);the National Natural Science Foundation of China(21905219);the National Natural Science Foundation of China(51932007);the National Natural Science Foundation of China(U1905215);the National Natural Science Foundation of China(21871217);the National Natural Science Foundation of China(U1705251);National Postdoctoral Program for Innovative Talents(BX20180231);China Postdoctoral Science Foundation(2020M672432);Hubei Postdoctoral Program for Innovative Research Post

摘要:

光催化二氧化碳还原成烃类化合物是解决能源短缺和环境污染的重要途径。而构建复合物光催化剂可以有效地解决单一光催化剂的缺点,并且提高二氧化碳还原活性。尽管对复合物光催化剂已经做了很多研究,然而对其活性增强的内在机制还缺乏理论认识。本文采用密度泛函理论计算方法研究了二维/二维BP/g-C3N4复合模型的电子性质和CO2还原反应过程。通过对能带位置和界面电子相互作用的综合分析发现,在BP/g-C3N4异质结中,光生载流子的迁移遵循S型异质结光催化机制。与单一的g-C3N4相比,这种异质结可以实现光生载流子的高效分离并且拥有良好的氧化还原能力。此外,通过对比研究CO2在g-C3N4和BP/g-C3N4还原反应过程发现,异质结使CO2还原反应的最大能垒从1.48 eV降低到1.22 eV。因此,BP/g-C3N4异质结在理论上被证明是一种优良的CO2还原光催化剂。这项工作有助于了解BP改性对g-C3N4光催化活性的影响,也为其他高性能CO2还原光催化剂的设计提供理论依据。

关键词: 光催化, CO2还原, S型异质结, g-C3N4, 理论计算

Abstract:

Photocatalytic reduction of CO2 to hydrocarbon compounds is a promising method for addressing energy shortages and environmental pollution. Considerable efforts have been devoted to exploring valid strategies to enhance photocatalytic efficiency. Among various modification methods, the hybridization of different photocatalysts is effective for addressing the shortcomings of a single photocatalyst and enhancing its CO2 reduction performance. In addition, metal-free materials such as g-C3N4 and black phosphorus (BP) are attractive because of their unique structures and electronic properties. Many experimental results have verified the superior photocatalytic activity of a BP/g-C3N4 composite. However, theoretical understanding of the intrinsic mechanism of the activity enhancement is still lacking. Herein, the geometric structures, optical absorption, electronic properties, and CO2 reduction reaction processes of 2D/2D BP/g-C3N4 composite models are investigated using density functional theory calculations. The composite model consists of a monolayer of BP and a tri-s-triazine-based monolayer of g-C3N4. Based on the calculated work function, it is inferred that electrons transfer from g-C3N4 to BP owing to the higher Fermi level of g-C3N4 compared with that of BP. Furthermore, the charge density difference suggests the formation of a built-in electric field at the interface, which is conducive to the separation of photogenerated electron-hole pairs. The optical absorption coefficient demonstrates that the light absorption of the composite is significantly higher than that of its single-component counterpart. Integrated analysis of the band edge potential and interfacial electronic interaction indicates that the migration of photogenerated charge carriers in the BP/g-C3N4 hybrid follows the S-scheme photocatalytic mechanism. Under visible-light irradiation, the photogenerated electrons on BP recombine with the photogenerated holes on g-C3N4, leaving photogenerated electrons and holes in the conduction band of g-C3N4 and the valence band of BP, respectively. Compared with pristine g-C3N4, this S-scheme heterojunction allows efficient separation of photogenerated charge carriers while effectively preserving strong redox abilities. Additionally, the possible reaction path for CO2 reduction on g-C3N4 and BP/g-C3N4 is discussed by computing the free energy of each step. It was found that CO2 reduction on the composite occurs most readily on the g-C3N4 side. The reaction path on the composite is different from that on g-C3N4. The heterojunction reduces the maximum energy barrier for CO2 reduction from 1.48 to 1.22 eV, following the optimal reaction path. Consequently, the BP/g-C3N4 heterojunction is theoretically proven to be an excellent CO2 reduction photocatalyst. This work is helpful for understanding the effect of BP modification on the photocatalytic activity of g-C3N4. It also provides a theoretical basis for the design of other high-performance CO2 reduction photocatalysts.

Key words: Photocatalysis, CO2 reduction, Step-scheme heterojunction, Graphitic carbon nitride, Density functional theory

MSC2000: 

  • O649