硝酸活化三聚氰胺前驱体对g-C3N4结构和可见光催化性能的影响

为缩短e-和h+的迁移途径而改善g-C3N4易发生光生载流子复合的缺陷,采用不同物质的量浓度的HNO3活化三聚氰胺前驱体,通过形成质子化氨基基团,制备了一系列x-HNO3-g-C3N4(x＝1,2,3,4,5 mol·L-1)光催化剂.采用N2物理吸附-脱附、X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TE...

Effect of Nitric Acid Activation Melamine Precursor on Structure and Visible-Light Photocatalytic Performance of g-C3N4

In order to shorten the migration pathway of e^- and h⁺ and improve the defect of recombination of photo-generated carriers in g-C₃N₄, this study used different molar concentrations of HNO₃ to activate melamine precursor, and formed a series of x-HNO₃-g-C₃N₄ (x=1, 2, 3, 4, 5 mol·L^-1) photocatalyst by forming a protonated amino group. In order to investigate the effect of the structure of the catalyst on its photocatalytic properties, all these above obtained photocatalysts were characterized by nitrogen gas adsorption-desorption isotherms, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), photoluminescence (PL), ultraviolet-visible diffuse reflection (UV-Vis DRS), transient photocurrent spectroscopy (TCS), electrochemical impedance spectroscopy (EIS), etc. The difference of visible light catalytic degradation activity of x-HNO₃-g-C₃N₄ and g-C₃N₄ obtained by direct calcination of melamine was studied with the using of rhodamine B (RhB) as a simulated dye contaminant. The resuts of experimental showed that the photocatalytic activity of 3 mol·L^-1-HNO₃-g-C₃N₄ was the highest. Compared with g-C₃N₄ obtained by directly calcining melamine, the degradation rate of RhB increased from 38% to 99% within 60 minutes. The 3 mol·L^-1-HNO₃-g-C₃N₄ catalyst was recycled 4 times, and the catalytic effect was still 99%. The high catalytic activity and stability of x-HNO₃-g-C₃N₄ can be explained as follows:after activation of HNO₃, the melamine precursor can make the g-C₃N₄ product prepared by thermal polymerization have a higher degree of polymerization, thereby a multi-layer g-C₃N₄ with large specific surface area was obtained. The PL results showed that the fluorescence intensity was significantly reduced, and the carrier lifetime was significantly improved. The EIS results showed that the carrier transport capacity was significantly enhanced, which improved the photocatalytic activity of g-C₃N₄.