Synthesis, Physicochemical and Electrochemical Characterization of TiO2 Nanotubes Arrays and Self-Standing Membranes as Susbtrate for Electro-Catalysts

TiO₂ nanotubes (NT) were synthesized by electrochemical anodization using 0.1 M NH₄F in ethylene-glycol and water by applying a two different potentials of 20 and 60 V during 0.5, 1, 2 and 4 h as anodization times. The material was thermally treated at 450°C under air atmosphere for 2h. TiO₂-NT membranes were produced by soaking as-prepared samples in ethanol. The material was characterized physicochemically by XRD, SEM, Raman spectroscopy and electrochemically by cyclic voltammetry. Current density behavior was monitored during material synthesis which is in agreement with anodization phases previously reported. SEM analysis allowed to confirm the morphology and measuring nanotubes length. In the case of the material prepared at 20 V, several morphologies clogged the surface. The nature of the TiO₂-NT in the underneath surface were confirmed by EDX. For the 60 V material, well-defined nanotubes were obtained which length varies depending on the anodization time from 6.35 to 46.0 μm. Nanotubes growth rate achieves a linear tendency after 1h and up to 4h of anodization. XRD pattern show that as-prepared samples are amorphous, while thermally-treated samples are crystalline (anatase phase). Raman spectroscopy information for the thermally treated samples was compared to that of the literature and is in well-agreement with previous reports. It also revealed that with both increasing, anodization time and potential, the crystallinity degree is affected. Finally, cyclic voltammetry was performed in a 0.5M H₂SO₄, N₂-saturated using a SCE and a Pt foil as reference and counter electrode, respectively. This electrochemical assessment showed that a capacity behavior is observed for these samples which increases directly proportional with anodization time.