TiO₂ Nanotubes: Synthesis and Applications

Abstract

TiO(2) is one of the most studied compounds in materials science. Owing to some outstanding properties it is used for instance in photocatalysis, dye-sensitized solar cells, and biomedical devices. In 1999, first reports showed the feasibility to grow highly ordered arrays of TiO(2) nanotubes by a simple but optimized electrochemical anodization of a titanium metal sheet. This finding stimulated intense research activities that focused on growth, modification, properties, and applications of these one-dimensional nanostructures. This review attempts to cover all these aspects, including underlying principles and key functional features of TiO(2), in a comprehensive way and also indicates potential future directions of the field.

Self-decoration of Pt metal particles on TiO2 nanotubes used for highly efficient photocatalytic H2 production

“…To produce these nanotube structures a Ti metal substrate can be anodized under self-organizing electrochemical conditions. 4 The advantage of an anodic formation is not only simplicity of the process but also the easiness of geometry control (length, diameter, wall thickness) via the selection of suitable anodization parameters. 4 In the context of H 2 production from TiO 2 , as co-catalysts most active are noble metal nanoparticles (mainly Pt) that act very efficiently on TiO 2 nanostructures -in fact in order to obtain measurable contents of H 2 from TiO 2 under non-biased conditions (without the use of a counter electrode and by applying a potential difference) co-catalyst decoration is mandatory.…”

“…4 The advantage of an anodic formation is not only simplicity of the process but also the easiness of geometry control (length, diameter, wall thickness) via the selection of suitable anodization parameters. 4 In the context of H 2 production from TiO 2 , as co-catalysts most active are noble metal nanoparticles (mainly Pt) that act very efficiently on TiO 2 nanostructures -in fact in order to obtain measurable contents of H 2 from TiO 2 under non-biased conditions (without the use of a counter electrode and by applying a potential difference) co-catalyst decoration is mandatory. [5][6][7] There are mainly two beneficial effects ascribed to Pt decoration: (i) changes in surface band bending in TiO 2 induced by the metal contact (Fermi level pinning) which leads to a faster transport of electrons, and (ii) its role as a hydrogen recombination catalyst that promotes H 2 formation from reduced atomic hydrogen.…”

Investigation of the mechanical and chemical characteristics of nanotubular and nano-pitted anodic films on grade 2 titanium dental implant materials

“…This idea is driven by the fact that through the precise control of the electrochemical process parameters homogenous nanotubular TiO2 arrays can be grown on titanium substrates, for instance on titanium foils [12]. The anodic growth of nanotubular TiO2 arrays can be a reliable method, provided that the process parameters are set in a suitable range that allows the production of uniform surfaces, which can be easily investigated in in vitro experimental settings, e.g.…”

“Black” TiO2 Nanotubes Formed by High-Energy Proton Implantation Show Noble-Metal-co-Catalyst Free Photocatalytic H2-Evolution

“…These charge carriers migrate in valence and conduction bands to the semiconductor surface where they react with water to form O 2 and H 2 , respectively. Thus hydrogen, the energy carrier of the future, could be produced using just water and sunlight.Key factors for an optimized conversion of water to H 2 are i) as complete as possible absorption of solar light (small band gap) while ii) still maintaining the thermodynamic driving force for water splitting (sufficiently large band-gap), including suitable band-edge positions relative to the water red-ox potentials, and iii) possibly most challenging -a sufficiently fast carrier transfer from semiconductor to water to obtain a reasonable reaction kinetics as opposed to carrier recombination or photo-corrosion [2][3][4][5][6][7].In spite of virtually countless investigations on a wide range of semiconductor materials that in many respects are superior to titania (mostly in view of solar light absorption and carrier transport), TiO 2 still remains one of the most investigated photocatalysts. This is only partially due to suitable energetics but more so because of its outstanding (photo-corrosion) stability [2][3][4][5][6][7].…”