New carbon nitride close to C_(6)N_(7) with superior visible light absorption for highly efficient photocatalysis  

具有接近C_(6)N_(7)结构和优异可见光吸收的新型氮化碳应用于高效光催化

作　　者：Xinyu Zhao Yingnan Zhao Huaqiao Tan Huiying Sun Xing Qin Wingkei Ho Min Zhou Jinliang Lin Yangguang Li 赵鑫宇;赵英男;谭华桥;孙慧颖;覃星;何永基;周敏;林锦良;李阳光(Key Laboratory of Polyoxometalate and Reticular Material Chemistry of Ministry of Education,Faculty of Chemistry Northeast Normal University,Changchun 130024,China;Department of Science and Environmental Studies,The Education University of Hong Kong,Hong Kong,China)

机构地区：[1]Key Laboratory of Polyoxometalate and Reticular Material Chemistry of Ministry of Education,Faculty of Chemistry Northeast Normal University,Changchun 130024,China [2]Department of Science and Environmental Studies,The Education University of Hong Kong,Hong Kong,China

出　　处：《Science Bulletin》2021年第17期1764-1772,M0004,共10页科学通报（英文版）

基　　金：supported by the National Key R&D Program of China (2020YFA0406101);the National Natural Science Foundation of China (21771033 and 22071020);the Fundamental Research Funds for the Central Universities (2412018BJ001 and 2412018ZD007);the “Hong Kong Scholar” Programme (XJ2018021);the General Research Fund;Research Grants Council of Hong Kong SAR Government (18301117);Dean’s Research Fund [04425], Ed UHK。

摘　　要：The rational design and construction of novel two-dimensional(2D)carbon nitrides(CNs)beyond g-C_(3)N_(4) is a hot topic in the fields of chemistry and materials.Inspired by the polymerisation of urea,we have prepared a series of novel C-C bridged heptazine CNs UO_(x)(where x is the ratio of urea to oxamide,x=1,1.5,2,2.5,and 3),which are similar to(C_(6)N_(7))n,upon the introduction of oxamide.As predicted using density functional theory(DFT)calculations,the conjugated structure of UO_(x) was effectively extended from an individual heptazine to the entire material.Consequently,its bandgap was reduced to 2.05 eV,and its absorption band edge was significantly extended to 600 nm.Furthermore,its carrier transfer and separation were significantly enhanced,establishing its superior photocatalytic activity.The optimised UO_(2) exhibits a superior photocatalytic hydrogen production rate about 108.59 lmol h^(-1)(using 10 mg of catalyst)with an apparent quantum efficiency(AQE)of 36.12%and 0.33%at 420 and 600 nm,respectively,which is one of the most active novel CNs reported to date.Moreover,UO_(2) exhibits excellent photocatalytic activity toward the oxidation of diphenylhydrazine to azobenzene with conversion and selectivity reaching~100%,which represents a promising highly efficient 2D CN material.Regarding phenols degradation,UO_(2) also displayed significantly higher activity and durability during the degradation of phenol when compared to traditional g-C_(3)N_(4),highlighting its significant potential for application in energy,environment and photocatalytic organic reactions.合理设计并制备新型氮化碳是化学和材料领域的研究热点.本文受尿素聚合的启发,以草酰二胺替代部分尿素制备了C-C桥联、结构接近C_(6)N_(7)的新型氮化碳UO_(x)(x为尿素与草酰二胺的物质的量之比,x=1、1.5、2、2.5和3).密度泛函理论计算表明,UO_(x)的共轭性由单个庚嗪环扩展到了整个材料框架.因此,其禁带宽度缩小到2.05 e V,吸收带边被大幅扩展到600 nm.此外,它的载流子传输和分离也得到显著增强,因而展现出优异的光催化活性.在一系列样品中,UO_(2)具有最佳的光催化活性,其光催化析氢速率约为108.59μmol h^(-1)(10mg催化剂),表观量子效率在420和600 nm下分别为36.12%和0.33%.此外,UO_(2)对二苯肼氧化以及酚类降解也呈现明显优于传统g-C_(3)N_(4)的优异光催化活性和稳定性,它是一类极具发展前景的新型二维材料.

关 键 词：Carbon nitride UREA OXAMIDE Photocatalytic hydrogen production Photocatalytic oxidation of diphenylhydrazine 

分 类 号：O643.36[理学—物理化学] O644.1[理学—化学]