Nanotech 2011

Increasing the Efficiency of Photocatalytic Water Treatment with Titanium Dioxide Nanoparticles by Control of Crystal Shape

D. Rickerby
European Commission Joint Research Centre, IT

Keywords: photocatalysis, particle size, crystal shape, water treatment

Abstract:

The most commonly employed photocatalytic material is titanium dioxide; anatase is the photocatalytically reactive phase. Highly dispersed anatase nanoparticles have a large specific surface area. However the reaction is inherently inefficient because only a very small fraction of the incident photons is actually used for photocatalysis. Various methods have therefore been proposed to increase the efficiency of the photocatalytic reaction. These include doping with gold to increase the photocatalytic activity and doping with nitrogen or boron to extend the useable wavelengths into the visible light range. Calculation of the particle shape and phase stability by means of a thermodynamic model shows that the morphology is dependent on particle size due to the increasing surface contribution to the free energy with decreasing size. Theoretically predicted crystal shapes correspond closely to those of nanoparticles synthesised under near-equilibrium conditions. Growth of stable (101} facets is favoured with respect to the reactive (001} facets due to minimization of the total free energy. Recent work has therefore been directed towards controlled growth of titanium dioxide crystals with a greater proportion of high energy facets in order to increase the photocatalytic efficiency.
 

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