摘要
石墨相氮化碳(g-C_(3)N_(4))是一种优异的产H_(2)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-C_(3)N_(4)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-C_(3)N_(4)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-C_(3)N_(4)纳米片显示出大幅提升的光催化产氢活性(2275.6μmol·h^(-1)·g^(-1)),分别是块状g-C_(3)N_(4)、D-A结构g-C_(3)N_(4)、g-C_(3)N_(4)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。
Photocatalytic hydrogen production is a promising strategy for utilizing inexhaustible solar energy as a source of clean energy.Graphitic carbon nitride(g-C_(3)N_(4))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-C_(3)N_(4) 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-C_(3)N_(4) 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-C_(3)N_(4) 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-C_(3)N_(4) 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-C_(3)N_(4) 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-C_(3)N_(4) nanosheet shows a considerably improved photocatalytic hydrogen production activity(2275.6μmol·h^(−1)·g^(−1)),which is 5.30,2.60,and 1.30 times that of bulk g-C_(3)N_(4),D-A structured bulk g-C_(3)N_(4),and g-C_(3)N_(4) nanosheet,respectively.This work offers a valuable strategy for developing D-A-modified photocatalytic materials for solar energy conversion.
作者
殷方鑫
秦品权
许景三
曹少文
Fangxin Yin;Pinquan Qin;Jingsan Xu;Shaowen Cao(State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology,Wuhan 430070,China;School of Science,Wuhan University of Technology,Wuhan 430070,China;School of Chemistry and Physics,Queensland University of Technology,Brisbane,QLD 4000,Australia)
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2023年第11期109-119,共11页
Acta Physico-Chimica Sinica
基金
国家重点研发计划(2022YFE0114800)
国家自然科学基金(51922081)资助项目。
作者简介
Corresponding authors:秦品权,Emails:qinpqcu@whut.edu.cn;Corresponding authors:曹少文,Emails:swcao@whut.edu.cn。
