Synthesis Of Graphene-TiO₂Nanotube And Its Photocatalytic Performance

TiO₂is an excellent semiconductor photocatalysts. but, at present, the preparedTiO₂nanoparticles have small specific surface area and the light response is weak inthe visible region. It is severely restricted their actual production applications.Therefore, how to increase its surface area, to prevent the agglomeration of particles,a significant reduction in electron-hole pair recombination rate, the TiO₂absorbslight district moves to larger wavelengths, these have become the barriers of puttingthe TiO₂into the practical application in the field of photocatalysis which must to beovercome. As emerging material graphene has unique electrical and opticalproperties, large surface area, etc., in order to provide the possibility to solve theabove problems.In this paper, under the conditions of concentrated alkali, we use the titaniumdioxide nanoparticle （P25） as precursor to prepared titanate nanotubes（NTN） byhydrothermal method, and using different temperatures to obtain a series of its finalcalcined titania nanotubes. Based on this, adding graphene as a precursor andsodium dodecylbenzenesulfonate as a surfactant, we synthesized the graphene-NTNcomposite catalyst by hydrothermal method. For the preparation of the compositecatalyst precursor we took three combinations of ways, first: TiO₂nanoparticles andgraphite oxide; second: NTN and graphite oxide; Third: TiO₂nanoparticles andgraphene; in all of these three modes, we added NaOH to make the solution in aconcentrated alkaline conditions. And the main role of NaOH is to change the shapeof TiO₂particles into a NTN, and restore graphite oxide into graphene. Theexperiments showed that the first combination is more efficient, so we choose thefirst way to prepare different proportion composite catalyst.The structure, morphology, composition and surface properties of theas-prepared catalysts were characterized with transform infrared spectroscopy（FT-IR）, X-ray diffraction（XRD）, nitrogen adsorption-desorption, scanning electronmicroscopy （SEM）, transmission electron microscopy（TEM）, UV-Vis-diffusereflectance spectroscopy（UV-Vis-DRS）. The results showed that as the increase ofcalcination temperature, the NTN shift from anatase to rutile phase, and thetube-shaped damaged seriously. When the temperature is700℃the NTN isessentially fragments, and the energy band gap decreases. The catalytic degradationof methylene blue degradation rate can reach65.4%and showed a higher activitywhen the calcination temperature is450℃and the samples obtained the UV lightfor120minutes. The first catalytic combination is more efficient, and when thecatalytic composite rate is10%, owns best performance. The photocatalytic degradation rate in the visible light is60.6%after4hours absorbing.