熔盐辅助法制备g-C3N4纳米结构及其光催化制氢性能

以尿素作为原料, 采用熔盐辅助热聚合法在KCl-NaCl-BaCl₂体系中制备了带隙可调的g-C₃N₄纳米结构. 采用X射线衍射仪、 扫描电子显微镜、 X射线光电子能谱仪、 紫外-可见漫反射光谱仪及荧光光谱仪对产物的结构、 形貌、 成分及光学性能进行了表征. 对g-C₃N₄纳米结构可见光条件下的光催化制氢性能进行了测试, 研究了不同的尿素/熔盐比对其光催化性能的影响. 结果表明, 熔盐辅助热聚合法制备的g-C₃N₄ 纳米结构吸收光谱出现明显宽化, 吸收边由普通热聚合法制备g-C₃N₄的约450 nm红移至约500 nm左右. 同时光生载流子复合几率明显降低, 从而有效提升其光催化制氢性能. 最优化的g-C₃N₄(60)样品析氢速率达到12301.1 μmol?g^?1?h^?1, 为普通热聚合法制备g-C₃N₄析氢速率的4倍.

Molten-salt-assistance Synthesis and Photocatalytic Hydrogen Evolution Performances of g-C3N4 Nanostructures

Using urea as raw material， g-C₃N₄ nanostructures with adjustable bandgap were prepared in KCl-NaCl-BaCl₂ system by molten-salt-assistance thermal polymerization method. The structure， morphology， composition and optical properties of the products were characterized by X-ray diffraction， scanning electron microscope， X-ray photoelectron spectrometer， UV-Visible diffuse reflection spectrometer and fluorescence spectrometer， respectively. The photocatalytic performance of the products in visible light was tested， and the effects of different urea/molten salt ratios on the photocatalytic performance of g-C₃N₄ nanostructures were studied. The results show that the absorption spectra of g-C₃N₄ nanostructure prepared by molten-salt- assistance thermal polymerization manifest obvious broadening， and the absorption edge shifts from ca. 450 nm to ca. 500 nm， compared with the g-C₃N₄ prepared by ordinary thermal polymerization method. At the same time， the recombination rate of photogenerated carriers is obviously reduced， so the photocatalytic hydrogen production performance is effectively improved. The hydrogen evolution rate of the optimized g-C₃N₄（60） samples reach 12301.1 μmol?g^?1?h^?1， which is 4 times that of g-C₃N₄ prepared by ordinary thermal polymerization method.