Modeling of Growth and Dissolution of Nanotubular Titania in Fluoride-Containing Electrolytes

In this paper, model calculations of diffusion processes and pH profiles inside TiO 2 nanotubes are performed in order to explore key factors in the growth mechanism of this system in aqueous electrolytes. An electrochemical steady state featured by an equivalent rate between oxide growth and dissolution is reached for a given current efficiency. Electrochemical oxide growth is found to be exclusively located at the pore bottom, whereas chemical oxide dissolution is uniformly distributed over the whole nanotube. It can be deduced from the results that electrolyte resistance or diffusion processes in the electrolyte inside the tubes are not limiting.