Electrochemical synthesis and applications of transparent titania layers

Titanium dioxide films represent promising materials for a wide range of applications, such as indoor and outdoor degradation of pollutants, self-cleaning surfaces, solar cells and optically transparent electrodes. However, the commercial application of these materials requires the development of new, industrially viable preparation techniques for the synthesis of mechanically robust and transparent TiO2 layers. Here, we present a simple and inexpensive electrochemically assisted procedure to deposit transparent and mechanically robust TiO2 films on various kinds of substrates, both conductive and non-conductive (glass slides, metal laminas, optically transparent conductive oxides). The obtained films were characterized for their morphology and thickness by scanning electron microscopy (SEM). Moreover, the film optical, mechanical and electrochemical properties were investigated by diffuse reflectance spectroscopy (DRS), mechanical tests (Wolf Wilburn hardness and adhesion tests), and cyclic voltammetry, respectively. The presented procedure gives rise to uniform and crack-free films, showing excellent chemical, mechanical, and electrochemical robustness. The obtained layers were compared to films prepared by a routine preparation technique (dip coating), exhibiting significantly improved morphological, optical and conductive properties. The photoelectrochemical properties of TiO2 films were exploited to fabricate a working Grätzel cell and to activate a photoelectrochemical polymerization of polypyrrole onto an un-conductive support. The obtained stable and transparent TiO2 films represent promising materials for numerous applications such as photocatalytic windows and coatings, antifogging mirrors, solar cells and optically transparent electrodes. With respect to classical commercial nano-powders, the present robust films reduce the health concerns associated with volatile nanostructured materials.