石墨相氮化碳纳米管的合成及光催化产氢性能

通过硬模板法,采用氰胺前驱物和二氧化硅纳米管(SiO₂-NTs)模板,合成石墨相氮化碳纳米管(CN-NTs)光催化剂。采用扫描电镜(SEM)、透射电镜(TEM)、X射线粉末衍射(XRD)、傅立叶变换红外光谱(FT-IR)、氮气吸附/脱附测试、紫外可见漫反射光谱(UV-Vis DRS)、荧光光谱、热重分析(TGA)等手段对CN-NTs催化剂的结构与性能进行表征。结果表明,CN-NTs的化学组成是石墨相氮化碳(g-C₃N₄),形貌为均匀的纳米管,且是介孔材料。与体相氮化碳(B-CN)和介孔石墨相氮化碳(mpg-CN)相比,CN-NTs的光吸收带边蓝移到440 nm,荧光发射谱的峰强减弱。在可见光(λ>420 nm)照射下,CN-NTs具有较高的光催化分解水活性,产氢速率为58 μmol/h,且表现出良好的光催化活性稳定性和化学结构稳定性。研究结果表明纳米管状结构能有效促进g-C₃N₄半导体激子解离,提高光生电子-空穴的分离效率,进而显著优化g-C₃N₄的光催化产氢性能。

Graphitic Carbon Nitride Nanotubes: Synthesis and Photocatalytic Activity for Hydrogen Evolution

Graphitic carbon nitride nanotubes (CN-NTs) photocatalyst has been synthesized by a hard-template method by using cyanamide as a precursor and silica nanotubes (SiO₂-NTs) as a hard template. The structure and properties of CN-NTs catalyst are characterized by the techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen absorption/desorption experiment, ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS), fluorescence spectra and thermogravimetric analysis (TGA). As demonstrated by the experimental results, CN-NTs possess the chemical structure of graphitic carbon nitride (g-C₃N₄) and the morphology of uniform nanotubes, and belong to mesoporous materials. Compared with the bulk carbon nitride (B-CN) and the mesoporous graphitic carbon nitride (mpg-CN), the optical absorption band edge of CN-NTs blue-shifts to 440 nm, and the peak intensity of the fluorescence emission spectra for CN-NTs reduces. With the visible light irradiation (λ>420 nm), CN-NTs show an outstanding photocatalytic water splitting activity with the hydrogen evolution rate of 58 μmol/h, and also demonstrate excellent stability in photocatalytic activity and chemical structure. The investigation results indicate that the nanotube structure effectively promotes the exciton separation of g-C₃N₄ semiconductor, and improves the separation efficiency of photogenerated electrons and holes, thus remarkably optimizing the photocatalytic activity of g-C₃N₄ toward hydrogen evolution.