The Anodization of Thin Titania Layers as a Facile Process towards Semitransparent and Ordered Electrode Material

Abstract

Photoanodes consisting of titania nanotubes (TNTs) grown on transparent conductive oxides (TCO) by anodic oxidation are being widely investigated as a low-cost alternative to silicon-based materials, e.g., in solar light-harvesting applications. Intending to enhance the optical properties of those photoanodes, the modification of the surface chemistry or control of the geometrical characteristics of developed TNTs has been explored. In this review, the recent advancement in light-harvesting properties of transparent anodic TNTs formed onto TCO is summarized. The physical deposition methods such as magnetron sputtering, pulsed laser deposition and electron beam evaporation are the most reported for the deposition of Ti film onto TCO, which are subsequently anodized. A concise description of methods utilized to improve the adhesion of the deposited film and achieve TNT layers without cracks and delamination after the anodization is outlined. Then, the different models describing the formation mechanism of anodic TNTs are discussed with particular focus on the impact of the deposited Ti film thickness on the adhesion of TNTs. Finally, the effects of the modifications of both the surface chemistry and morphological features of materials on their photocatalyst and photovoltaic performances are discussed. For each section, experimental results obtained by different research groups are evoked.

Nanostructured Semi-Transparent TiO2 Nanoparticle Coatings Produced by Magnetron-Based Gas Aggregation Source

“…Because of this, various approaches that allow the production of nanostructured TiO 2 coatings were reported in the literature. Although most of them utilize chemical processes such as template-assisted sol-gel [6,7] or anodization [8][9][10], there is an increasing interest in the physical ways of synthesis of nanostructured titania that enables solvent-free production of high-purity TiO 2 nanostructured coatings. Among them, two distinct vacuum-based strategies were identified to be highly advantageous-glancing angle deposition (GLAD) and techniques based on the gas-phase synthesis of nanoparticles by magnetron-based gas aggregation sources (m-GAS).…”