Influence of sintering temperature, pressing, and conformal coatings on electron diffusion in electrophoretically deposited porous TiO2

The electrophoretic deposition of nanoporous TiO2 layers allows us to investigate separately the influence of sintering temperature, porosity, and conformal surface coatings on the effective diffusion coefficient (D-eff) of excess electrons in porous layers. Photocurrent transients were measured to obtain D-eff in nanoporous TiO2 layers immersed in aqueous electrolyte. The applied treatments control parameters such as the contact between interconnected nanoparticles, the coordination of nanoparticles in the porous network, and the surface passivation of TiO2 nanoparticles. The hierarchy of the different factors for transport optimization in porous TiO2 is discussed. Under fixed geometry of the nanoporous network, trapping on surface states can strongly limit electron diffusion in porous TiO2. (c) 2006 American Institute of Physics.