Effect of Chemical Polishing on the Formation of TiO2 Nanotube Arrays Using Ti Mesh as a Raw Material

As a unique form of TiO₂, TiO₂ nanotube arrays (TiO₂NTAs) have been widely used. TiO₂NTAs are usually prepared by Ti foil, with little research reporting its preparation by Ti mesh. In this paper, TiO₂NTAs are prepared on a Ti mesh surface via an anodic oxidation method in the F-containing electrolyte. The optimal parameters for the synthesis of TiO₂NTAs are as follows: the solvent is ethylene glycol and water; the electrolyte is NH₄F (0.175 mol/L); the voltage is 20 V; and the anodic oxidation time is 40 min without chemical polishing. However, there is a strange phenomenon where the nanotube arrays grow only at the intersection of Ti wires, which may be caused by chemical polishing, and the other areas, where TiO₂NTAs cannot be observed on the surface of Ti mesh, are covered by a dense TiO₂ film. New impurities (the hydrate of TiO₂ or other products) introduced by chemical polishing and attaching to the surface of the Ti mesh reduce the current of anodic oxidation and further inhibit the growth of TiO₂ nanotubes. Hence, under laboratory conditions, for commercially well-preserved Ti mesh, there is no necessity for chemical polishing. The formation of TiO₂NTAs includes growth and crystallization processes. For the growth process, F^- ions corrode the dense TiO₂ film on the surface of Ti mesh to form soluble complexes ([TiF₆]^2-), and the tiny pores remain on the surface of Ti mesh. Given the basic photoelectrochemical measurements, TiO₂NTAs without chemical polishing have better properties.