Preparation, Modification And Photocatalytic Propeties Of Protonic Titanate Nanotubes

Titanium dioxide has been widely applied in the field of solar cell, gas sensingmaterial, degradation of pollutants, etc, as a lost cost, physical and chemical stabilitysemiconductor material. Most researchers study titanium dioxide because in the fieldof photocatalysis, titanium dioxide can degrade most of organic pollutants. However,titanium dioxide has two defects as photocatalyst, one is the high recombination rateof photo-induced electron-hole pairs formed in photocatalytic processes: another isthe absorption capability to visible light photocatalytic. Therefore, numerous studieshave been recently performed to improve the efficiency of photocatalytic reactions.The methods are used to be introduced in modifying TiO2to suppress thephtot-induced electron-hole recombination and broaden the region of photo-respone.In this paper the protonic titanate nanatubes are synthesized by a simple one-setphydrothermal method, the samples are modified via the ion-exchanges process. Thecapability of the ion-exchangs and the optical properties of materials are studied.Protonic titanate nanotubes are prepared by hydrothemal method and thenclacinated to obtain TiO2nanometer materials. Transmission electron microscopy(TEM), x-ray diffraction (XRD) and photocatalytic reaction were carried tocharacterize their morphology, crystallization and photocatalytic activity. Theexperiment results have shown that all samples of crystal were anatase phase. Whenthe heat treatment temperature from300℃to600℃，with the improvement of thecalcination temperature, the crystallization of the samples was improved obviously.When the calcination temperature was below400℃, the morphology of the samplematained tubular structure, however, the tublar structure are destroyed and thentransform nanoparticles, with the calcination temperature increasing. In order toevaluate the photocatalytic activity of the sample, we use UV light source to evaluate the photocatalytic activity of the catalyst for the degradation of menthyl orange. Theresult shows that the sample calcined at600℃for90min, acid washing for2h hasbetter phtotcatalytic performance for degradation of menthyl orange.Using protonic titanate nanotubes (H-TNT) prepared via hydrothermal method asthe precursor templates，[Pd(NH3)4]2+intercalacted H-TNT are prepared byion-exchanges reaction under alkaline conditions. The samples are characterized byICAP, XRD, TEM, DRS and XPS. The effect of the concentrations of [Pd(NH3)4]2+and pH on the performance of the ion-exchanges of H-TNT are discussed, meanwhile,the crystallization, morphology, optical properties and the chemical composition ofthe samples are also investigated. The experiment results show that [Pd(NH3)4]2+existed in the surface of H-TNT. The palladium and oxygen atoms are attracted eachother，and subsequently forming a link called Pd-O bond. After [Pd(NH3)4]2+areintercalated H-TNT, the crystallization and morphology of Pd-TNT are no change,however, the capability of optical absorption of Pd-TNT is better than H-TNT within400nm-600nm. The concentrations of [Pd(NH3)4]2+and pH influence theperformance of the ion-exchanges of H-TNT. When the concentrations of[Pd(NH3)4]2+is small and the mass ratios of Pd and H-TNT in the reaction solution issmall,[Pd(NH3)4]2+can load on H-TNT completely within pH range from9to12.When the concentrations of [Pd(NH3)4]2+is large and the mass ratios of Pd andH-TNT in the reaction solution is large, the load ratios of [Pd(NH3)4]2+increase withthe concentrations of [Pd(NH3)4]2+and pH increasing. But when pH is greater than orequal to10, the load ratios of [Pd(NH3)4]2+tend to be almost unchanged.And then the effect of the load ratios of Pd and the calcination temperature onthe crystallization, morphology and optical properties is discussed. The results haveshown that when the load ratio of Pd is14.32%, we can detect the presence of PdO inXRD patterns. Nanotubes are changed into nanoparticles, with the calcinationtemperature increasing. With the load ratios of Pd and the calcination temperatureincreasing, the absorption of visible light of the samples is enhanced than before. Onthe phtotcatalytic performance,1.01%Pd-TNT calcined at500℃show the best photocatalytic activity, the reaction rate was nearly five times than before. Thedegradation rate of methyl orange reach99.8%under UV light irradiation for90min,meanwhile, the degradation rate of methyl orange is58.8%under visible lightirradiation for360min.