摘要
通过人工光催化将水分解为可再生的氢能燃料,是解决全球能源问题的重要途径之一.石墨氮化碳(g-C_(3)N_(4))作为一种极具发展前景的新型半导体光催化剂,因其成本低、能带位置合适和化学稳定性好等优点受到广泛研究.为了克服原始g-C_(3)N_(4)光生电荷易复合和电导率低等缺点,从而提高光催化析氢效率,研究人员通过纳米结构设计、增大比表面积、负载单原子和掺杂元素等方法改善g-C_(3)N_(4)基光催化剂的性能.然而,由于脱胺不完全导致石墨氮化碳层内载流子难以迁移,仍旧极大地限制了其可见光利用率.因此,如何有效改善载流子传输,构建新的电子迁移通道依然需要探索和研究.本文采用热聚合法制备g-C_(3)N_(4)(CN-C),将碳元素以碳环的形式逐渐渗透到结晶氮化碳表面,从而实现光生电子在内层和外层之间的快速空间转移,并运用高分辨透射电镜(HRTEM)、二次离子质谱(SIMS)、密度泛函理论(DFT)和飞秒瞬态吸收光谱(fs-TA)等手段研究了所制备半导体材料的结构和光催化机理.HRTEM结果表明了氮化碳与碳环的晶格条纹的存在,证实了结晶氮化碳与碳环的形成.SIMS通过对碳和氮元素在制备的光催化剂的不同深度的比值分析证实了碳环的分布,表明碳环成功从氮化碳表面渗透.DFT结果表明,分子中的内层和外层产生不同的费米能级形成S型同质结并在氮化碳内部建立了的内置电场,从而有效地消除了由于丰富的界面缺陷引起的载流子陷阱的影响,并抑制光生载流子的复合.CN-C内层与外层形成的S型同质结在界面的两侧诱导能级弯曲,形成层间电荷转移通道.此外,fs-TA结果证明碳环与氮化碳结合的共轭平面内也形成了面内光生电荷转移通道,这种双向电子转移通道极大地提高了光生电子解离效率,制备的CN-C在光催化析氢的最大量子效率为15.56%.由此可见,在结晶氮化碳内部成功构
Enhancing the carrier separation in graphitized carbon nitride(g‐C_(3)N_(4))is advantageous for improving its photocatalytic activity.Herein,we propose a feasible method for preparing CN‐C by thermal polymerization to gradually infiltrate carbon rings(C‐rings)into the surface of crystalline carbon nitride(CN),enabling photogenerated electrons to be transferred rapidly between the CN inner layers and the CN/C outer layer.Successful penetration and distribution of carbon rings into carbon nitride were confirmed by secondary ion mass spectroscopy using ratio analysis of C and N elements at various depths of the prepared photocatalyst.Theoretical calculations indicated that CN and CN/C in the molecule generated different Fermi levels to form an S‐scheme homojunction,establishing appropriate built‐in electric fields and thus enabling interlayer charge migration.Moreover,the overlap of the conjugate plane of C‐rings with carbon nitride led to the formation of photogenerated in‐plane charge transfer tunnels.The two‐electron transfer tunnels greatly improved the dissociation efficiency of photogenerated electrons.The prepared sample loaded with 3 wt%Pt as a co‐catalyst for hydrogen production under visible light irradiation,and the prepared optimal sample CN‐C showed a maximum quantum efficiency of 15.56%for photocatalytic H_(2)evolution at 385 nm.This research introduces a new idea for constructing a directional transfer path for charge carriers in‐plane and intralayer.
作者
余治晗
关晨
岳晓阳
向全军
Zhihan Yu;Chen Guan;Xiaoyang Yue;Quanjun Xiang(State Key Laboratory of Electronic Thin Film and Integrated Devices,School of Electronic Science and Engineering,University of Electronic Science and Technology of China,Chengdu 610054,Sichuan,China;Yangtze Delta Region Institute(Huzhou),University of Electronic Science and Technology of China,Huzhou 313001,Zhejiang,China)
基金
国家自然科学基金(22272019)
四川省科技计划(2022ZYD0039,2022JDRC0096,2022NSFSC1213,2022NSFSC0870,2023NSFSC1069)
电子薄膜与集成器件国家重点实验室开放基金(KFJJ202105).
关键词
碳环
S型结构
层间电荷转移
同质结
光催化析氢
Carbon ring
S‐scheme
Interlayer charge transfer
Homojunction
Photocatalytic hydrogen evolution
reaction
