Synthesis Of Titanium Dioxide Based Nanocomposite And Photocatalytic Activities

Titanium dioxide (TiO2) photocatalyst has been widely used in water pollution remediation, solar cell and sensor, etc. However, TiO2is active only in the ultraviolet region (λ<387nm) due to its wide band gap (3.2eV). TiO2has a poor adsorption ability. The photogenerated electron-hole always combines easily before transfer to the surface of TiO2. So, Much attention was paid to search for promising ways to broaden the absorption range and to increase the separation rate of photogenerated electrons and holes of TiO2, such as metallic and nonmetallic elements doping, combining TiO2with narrow band gap semiconductors or conductive materials, and morphology control. Graphene/Ni/TiO2/CNTs and g-C3N4/TiO2/CNTs nanocomposites were designed and prepared in this paper, and used to degrade organic pollutant under UV and visible light.1. Synthesis of graphene/Ni/TiO2/CNTs nanocomposite and photocatalytic activitiesThe graphene/Ni/TiO2/CNTs nanocomposite was fabricated. Firstly, the TiO2nanoparticles doped with nickel were coated on graphene by solvo-thermal method. Then the CNTs were grown by in-situ chemical vapor deposition using the nickel as catalyst. The prepared graphene/Ni/TiO2/CNTs nanocomposite photocatalyst was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and Raman spectra. The photocatalytic activities of the samples were investigated by the photocatalytic degradation of methyl orange under UV and visible light respectively. The results indicated that the doping Ni in TiO2helped to enhance the photocatalytic activity of Ni/TiO2slightly. In the graphene/Ni/TiO2nanocomposite photocatalyst, graphene provided an efficient way for the photogenerated electrons to conduct out, which made its photocatalytic activity higher than Ni/TiO2. In graphene/Ni/TiO2/CNTs, the in-situ CNTs was grown between TiO2nanoparticles with metal Ni as active catalytic centers, and became another efficient way to separate the photogenerated electron-hole pairs, which made the photocatalytic performance of graphene/Ni/TiO2/CNTs more excellent than graphene/Ni/TiO2. Besides, the photocatalytic activities of graphene/Ni/TiO2/CNTs increased with graphene content in it.2. Synthesis of g-C3N4/TiO2/CNTs nanocomposite and photocatalytic activitiesGraphitic carbon nitride (g-C3N4) based composites have attracted much attention in recent years, owning to the excellent photoelectrochemical properties and important applications in new energy and the environment field. In this paper, the g-nanocomposites have been fabricated via a facile coating process of TiO2and a following in-situ growth of CNTs on TiO2doped with Ni. The photocatalytic performance test was carried out by the degradation of methyl orange under UV and visible light. The experimental results show that the degradation rate of g-C3N4/TiO2nanocomposite is2.4and1.7times higher than g-C3N4under UV and visible light respectively. The heterojunction interfaces in g-C3N4/TiO2and the in-situ CNTs facilitate the separation of photogenerated electron-hole pairs, which makes the photocatalytic performance of g-C2N4/TiO2/CNTs more excellent than g-C3N4/Ti02.