物理化学学报 >> 2023, Vol. 39 >> Issue (11): 2212062.doi: 10.3866/PKU.WHXB202212062

所属专题： 多物理场能源催化转化

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亚甲基蓝嵌入的供体受体型g-C3N4纳米片光催化剂用于产H2

殷方鑫1, 秦品权2,*(), 许景三3, 曹少文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 武汉理工大学, 理学院, 武汉 430070
    3 昆士兰科技大学, 化学和物理学院, 澳大利亚 布里斯班 QLD 4000
  • 收稿日期:2022-12-31 录用日期:2023-02-27 发布日期:2023-03-09
  • 通讯作者: 秦品权,曹少文 E-mail:qinpqcu@whut.edu.cn;swcao@whut.edu.cn
  • 基金资助:
    国家重点研发计划(2022YFE0114800);国家自然科学基金(51922081)

Methylene Blue Incorporated Donor-Acceptor g-C3N4 Nanosheet Photocatalyst for H2 Production

Fangxin Yin1, Pinquan Qin2,*(), Jingsan Xu3, Shaowen Cao1,*()   

  1. 1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China
    2 School of Science, Wuhan University of Technology, Wuhan 430070, China
    3 School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4000, Australia
  • Received:2022-12-31 Accepted:2023-02-27 Published:2023-03-09
  • Contact: Pinquan Qin, Shaowen Cao E-mail:qinpqcu@whut.edu.cn;swcao@whut.edu.cn
  • Supported by:
    the National Key R & D Program of China(2022YFE0114800);the National Natural Science Foundation of China(51922081)

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摘要：

石墨相氮化碳(g-C3N4)是一种优异的产H2光催化剂，但是其存在载流子分离效率低、光吸收能力较差和比表面积小的问题。本研究通过对二氰二胺和亚甲基蓝(MB)进行热共聚合，结合后续热剥离策略，成功合成了一种新型分子内供体-受体(D-A)结构g-C3N4纳米片光催化剂。实验结果和密度泛函理论(DFT)计算表明，将亚甲基蓝掺入g-C3N4框架中扩大了光吸收范围，促进了载流子的分离。此外，热剥离增加了催化剂的比表面积且进一步促进了载流子的分离。因此，D-A结构g-C3N4纳米片显示出大幅提升的光催化产氢活性(2275.6 μmol·h−1·g−1)，分别是块状g-C3N4、D-A结构g-C3N4、g-C3N4纳米片的5.30，2.60和1.30倍。这项工作为设计用于太阳能转换的D-A改性光催化材料提供了一个有价值的思路。

关键词: 供体-受体, 亚甲基蓝, g-C3N4纳米片, 光催化产氢

Abstract:

Photocatalytic hydrogen production is a promising strategy for utilizing inexhaustible solar energy as a source of clean energy. Graphitic carbon nitride (g-C3N4) is a widely used photocatalytic material in photocatalytic hydrogen production because of its simple preparation process, suitable band structure, and high stability. However, the low charge carrier separation efficiency and small specific surface area of pristine g-C3N4 restrict its photocatalytic activity. It has been demonstrated that the construction of intramolecular donor-acceptor (D-A) systems and ultra-thin nanosheet structures are effective strategies for enhancing the photocatalytic activity of g-C3N4. Herein, an intramolecular D-A structured g-C3N4 nanosheet photocatalyst is synthesized through the thermal copolymerization of dicyandiamide and methylene blue (MB), followed by thermal exfoliation. X-ray diffraction, Fourier transform infrared spectrometry, solid-state 13C nuclear magnetic resonance, and X-ray photoelectron spectroscopy analyses reveal that MB is successfully incorporated into the g-C3N4 framework and well retained after thermal exfoliation. The resulting D-A system induces intramolecular charge transfer from the donor units (MB segment) to the acceptor units (tri-s-triazine rings) and extends the absorption edge to approximately 500 nm. The ultra-thin nanosheet structure produced by thermal exfoliation shortens the charge transfer distance from the interior to the surface of g-C3N4 and reduces the charge transfer resistance, which increases the charge carrier separation efficiency. Furthermore, the introduction of MB generates a flaky structure during copolymerization, which promotes thermal exfoliation and results in a remarkably increased specific surface area. The transient photocurrent response, electrochemical impedance spectra, and time-resolved photoluminescence decay spectra reveal that the charge transfer and separation of g-C3N4 are further promoted by integrating the intramolecular D-A system and ultra-thin nanosheet structure. Density functional theory calculations further demonstrate that MB donates electrons to tri-s-triazine rings (electron acceptor). Moreover, the highest occupied molecular orbit of D-A structured g-C3N4 is mostly distributed around the MB segment, while the lowest unoccupied molecular orbit is distributed around tri-s-triazine rings, resulting in spatially separated photogenerated electron-hole pairs. Through integrating the intramolecular D-A system and ultra-thin nanosheet structure, the obtained photocatalyst exhibits enhanced charge carrier separation, an extended absorption edge, and enlarged specific surface area. As a consequence, the D-A structured g-C3N4 nanosheet shows a considerably improved photocatalytic hydrogen production activity (2275.6 μmol·h−1·g−1), which is 5.30, 2.60, and 1.30 times that of bulk g-C3N4, D-A structured bulk g-C3N4, and g-C3N4 nanosheet, respectively. This work offers a valuable strategy for developing D-A-modified photocatalytic materials for solar energy conversion.

Key words: Donor-acceptor, Methylene blue, g-C3N4 nanosheet, Photocatalytic hydrogen production