Materials for Energy, Efficiency and Sustainability: TechConnect Briefs 2015Materials for Energy, Efficiency and Sustainability TechConnect Briefs 2015

Water Technologies Chapter 8

Advanced oxidation processes for water purification: compact vs nanoporous anodic TiO2

V. Piazza, M.V. Diamanti, A. Mazare, MP. Pedeferri, P. Schmuki
Politecnico di Milano, Italy

pp. 283 - 286

Keywords: photocatalysis, titanium dioxide, nanotubes, anodic oxidation

In the last years, research on TiO2 engineering has been dedicated mostly to thin films for environmental and energetic applications, such as advanced oxidation processes for water purification and dye-sensitized solar cells. Anodic oxidation can effectively control oxide characteristics as a function of process parameters; in particular, the main features driving oxide photoefficiency are crystallinity and surface area. In high voltage anodizing, TiO2 nanocrystals generate in an otherwise amorphous oxide, owing to localized microplasma states. Conversely, nanotubular oxides have enhanced surface area but amorphous structure: annealing can induce partial crystallization, making their use successful in photocatalytic applications. Here we present a comparison among differently obtained anodic titanium oxides, in order to define the most effective and robust treatments for the production of photocatalytic layers for water purification. Results of organic dye degradation show a clear increase in photocatalytic efficiency with specific surface area, for a given crystallinity. Yet, microplasma on formerly compact oxides causes the formation of disordered nanopores, as well as oxide crystallization, leading to an efficiency only 20% lower than that of nanotubular oxides, even without annealing. A wide analysis of anodizing parameters was performed to provide a comprehensive correlation between oxides characteristics and performances in water purification.