Preparation And Photocatalytic Properties Of Graphite Phase Carbon Nitride

The semiconductor photocatalytic technology has been developed rapidy in recent years.Graphite phase carbon nitride (g-C3N4), a metal-free photocatalyst has been drawn much attentionbecause of its non-toxic、 high catalytic activity、excellent chemical stability, and the uniqueadvantages of electronic band structure. But due to the material properties of the polymer, theg-C3N4photocatalyst has some problems, such as small specific surface area, recombination ofgenerated electron-hole serious, low quantum efficiency and larger band gap, inefficiency use ofsolar etc, which restrict its application in energy and environmental photocatalysis. Therefore, inorder to make a better use of sunlight, preparing g-C3N4optimized and modified to obtain a highervisible light responsive is necessary.In this paper, graphite phase carbon nitride (g-C3N4) was prepared by two kinds of simplemethods. Meanwhile, XRD、UV-Vis、SEM、TEM、BET、TGA and other experimental methodswere used to study the effects of different preparation conditions on the structure and catalyticproperties of g-C3N4. Some conclusions have been made as follows:(1) A metal-free photocatalyst g-C3N4with layer structure was prepared by calciningdicyandiamide, showing high visible-light photocatalytic activity for the degradation of methylorange in water. X-ray diffractometer (XRD)、scanning electron microscope (SEM) and highresolution transmission electron microscopy (HRTEM) were used to characterize the structure ofphotocatalyst g-C3N4. The results indicate that the photocatalyst is graphite-like carbon nitride andthe size of the particles is about5-7nm. The spectrum of UV-vis absorption indicates that theabsorption edge of the g-C3N4was460nm，corresponding to the band gap energy of2.7eV. Thedegradation experiments of methyl orange in water show that its degradation efficiency can reach86.2%in2.5h. The photocatalytic mechanism experiments indicate that h+and O-2play a majorrole in the degradation of methyl orange in water.(2) A photocatalyst g-C3N4with nanorod morphology was prepared by hydrothermal inacetonitrile with cyanuric chloride and melamine. X-ray diffractometer (XRD), scanning electron microscope (SEM) and UV-Visible diffuse reflectance spectroscopy（UV-Vis） were used tocharacterize the structure of photocatalyst g-C3N4. The results indicate that the width and length ofg-C3N4nanorod are about25nm and1μm. Absorption edge of the g-C3N4is about650nm,corresponding to the bandgap energy of1.91eV. The degradation experiments of methyl orangeshow that its degradation efficiency can reach99.7%in2.5h.(3) Dicyandiamide was used to instead of melamine to prepare graphite phase carbon nitridenanosphere. The results of analysis indicate that the photocatalyst is graphite phase carbon nitrideand the size of the nanoball is about200nm. The spectrum of UV-Vis absorption indicates that theabsorption edge of the g-C3N4is590nm, corresponding to the bandgap energy of2.1eV. Thedegradation experiments of methyl orange show that its degradation efficiency can reach99.8%in2.5h.