自组装超分子前驱体制备g-C_(3)N_(4)及其光催化分解水产氢的研究

Preparation of g-C_(3)N_(4) by self-assembled supramolecular precursor and its study of hydrogen production from photocatalytic water splitting

光催化剂的结构调控对提高光催化效率有重要意义。以三聚氰胺为原料制备了g-C_(3)N_(4),并以三聚氰胺-三聚氰酸超分子为前驱体,制备了一系列MCx-g-C_(3)N_(4)(x为三聚氰胺与三聚氰酸的物质的量比,x=1、2、3或4)。采用XRD、FT-IR、SEM、TEM、N_(2)吸/脱附和XPS等对g-C_(3)N_(4)和MCx-g-C_(3)N_(4)进行了表征,发现g-C_(3)N_(4)和MCx-g-C_(3)N_(4)具有不同的形貌、结构、组成和比表面积。其中,MC3-g-C_(3)N_(4)为多孔的纳米片结构,n(C元素):n(N元素)为1.23,比表面积为45.63 m^(2)/g,是g-C_(3)N_(4)比表面积的4.5倍。以Pt为助催化剂,三乙醇胺为牺牲剂,在可见光下(≥400 nm)考察了催化剂的光催化分解水产氢性能。结果表明,MC3-g-C_(3)N_(4)表现出最佳的光催化分解水产氢性能,其产氢速率达到1127.83μmol/(h·g),是g-C_(3)N_(4)的35倍。MC3-g-C_(3)N_(4)较大的比表面积和多孔结构为反应提供了更多的活性位点,且纳米片结构缩短了光生电子迁移到催化剂表面的距离,促进了光生电子和空穴的分离,从而显著提高了其光催化分解水产氢性能。

The structural regulation of photocatalysts is important to improve the efficiency of photocatalysis.g-C_(3)N_(4) was prepared from melamine as raw material,and a series of MCx-g-C_(3)N_4(x is the molar ratio of melamine to cyanuric acid,and x = 1,2,3 or 4) catalysts were prepared using melamine-cyanuric acid supramolecular as precursor.XRD,FT-IR,SEM,TEM,N_(2) adsorption/desorption,and XPS were used to characterize g-C_(3)N_(4) and MCx-g-C_(3)N_4,and it is found that g-C_(3)N_(4) and MCx-g-C_(3)N_(4) exhibit different morphologies,structures,compositions and specific surface areas.Among them,MC3-g-C_(3)N_(4) displays porous nanosheet structure with n(C element):n(N element) of 1.23,and the specific surface area is 45.63 m^(2)/g,which is 4.5 times larger than that of g-C_(3)N_4.Using Pt as the co-catalyst and triethanolamine as the sacrificial agent,the catalytic performance of catalysts for hydrogen production from photocatalytic water splitting was investigated under visible light(≥ 400 nm).The results show that MC3-g-C_(3)N_(4) shows the best catalytic performance for hydrogen production from photocatalytic water splitting,and its hydrogen production rate reaches 1127.83 μmol/(h·g),which is 35 times higher than that of g-C_(3)N_(4).The large surface area and porous structure of MC3-g-C_(3)N_(4) provide more active sites for the reaction,and the nanosheet structure shorens the migration distance of photogenerated electrons to the catalyst surface,which promotes the separation of photogenerated electrons and holes,and thus significantly improving its catalytic performance for hydrogen production from photocatalytic water splitting.