Comparison of optical and electrochemical properties of anatase and brookite TiO2 synthesized by the sol–gel method

Three polymorphs of TiO2, rutile, anatase and brookite, are well known. Each variety has its own physical properties, bandgap, surface states, etc. For photovoltaic applications, anatase is the phase most used. Up to now, the third polymorph of TiO2, brookite, could not be obtained by soft chemistry methods. We have now synthesized nanometric particles of pure brookite by ‘chimie douce’ in aqueous solution. For the first time, this phase will be characterized in view of its possible application in dye-sensitized cells. We discuss the potential of brookite as a good candidate for photovoltaic devices in comparison to other phases, in terms of its morphology, bandgap and electrochemical properties in water and acetonitrile before sensitization.