Fabrication And Photocatalytic Properties Of Ti Net-based TiO₂Nanotubes By Anodization

In this study, titania nanotubes are anodized in the titanium net, and thenitrogen-doped nanotubes are obtained by ion implantation. The morphology,crystalline structure, chemical composition, microstructure and photocatalyticproperties of the nanotubes and the N-doped ones are discussed.The different morphologies of nanostructure are fabricated in Ti net byanodization combined with different technological processes. SEM shows thatridge-like nanostructures including nanopores and naonotubes on Ti net areradial pattern. However, of all processes, Ti net is mainly coated by nanotubeswhich is fabricated without chemical polishing pretreatment. On the top of theridge, part of the nanotubes are flattened, which can be wiped off afer ultrasonicvibration and the dependent and complete nanotubes are obtained. It is obviousthat without chemical polishing, the fabrication processing is simplified. Theaverage inner pore diameter calculated from the SEM images is between80nmand120nm, wall thickness30to45nm and tube length upon4μm.The GXRD results indicate that TiO₂nanotubes is amorphous beforeannealing. It can be seen that the crystalline nanotubes occurs in anatase at atemperature of450℃. Anatase transformed into rutile between450℃and550℃annealing.With the rising of the temperature,the content of the rutile increase.Compared with the samples with ultrasonic final treatment, the weight fractionof rutile with stirring is more.The TEM results reveal that, annealing at550℃, the single nanotube isanatase and the oxide on the surface consist of polycrystalline particles withboth anatase and rutile phase. It is found that defects like stacking faults aregenerated from the surface after ion implantation. The XPS patterns shows thatthere are three kinds of elements including tinanium, oxygen and carbon in thesurface of the nanotube and after ion implantation adding nitrogen. The high-resolution titanium2p peaks measured mathematically by means of the curvefitting technique indicate the presence of Ti⁴⁺and Ti³⁺. The photocatalyticproperties of the TiO₂nanotubes are improved by introducing Ti³⁺,whoseexsistence decreasing the recombination of the photo-generated carrierer. Themorphology and crystalline structure of the nanotubes doping nitrogen atdifferent implantation voltage and implantation dose are considered. The resultssuggest that implantation have little effect on the morphology and crystallinestructure.The photocatalytic degradation of RhB shows that the crystalline nanotubes mixed anatase and an optimal rutile phase have the highest photocatalyticproperties with the Rh B removal rate77.6%after120min irradiation. Comparedto the nanotubes made on the Ti foil, the photocatalytic properties of the samesize Ti net based nanotubes is higher. Because of the increasing of the photo-generate carrier recombination after N doping,the photocatalytic efficiencyunder the UV light decrease to40%.