Abstract
A simple route towards nanostructured mesoporous Indium-Tin Oxide (templated nano-ITO) electrodes exhibiting both high conductivities and optimized bicontinuous pore-solid network is reported. The ITO films are first produced as an X-ray-amorphous, high surface area material, by adapting recently established template-directed sol-gel methods using Sn(IV) and In(III) salts. Carefully controlled temperature/atmosphere treatments convert the as-synthesized ITO films into nano-crystalline coatings with the cubic bixbyite structure. Specially, a multi-layered synthesis was successfully undertaken for tuning the film thickness. In order to evaluate the performances of templated nano-ITO as an electrode substrate for photoelectrochemical applications, photoelectrodes were prepared by covalent grafting of a redox-active dye, the complex [Ru(bpy)(2)(4,4'-(CH(2)PO(3)H(2))(2)-bpy)]Cl(2)1 (bpy=bipyridine). Surface coverage was shown to increase with the film thickness, from 0.7 × 10(-9) mol.cm(-2) (one layer, 45 nm) to 3.5 × 10(-9) mol.cm(-2) (ten layers, 470 nm), the latter value being ~ 100 times larger than that for commercially available planar ITO. In the presence of an electron mediator, photocurrents up to 50 μA.cm(-2) have been measured under visible light irradiation, demonstrating the potential of this new templated nano-ITO preparation for the construction of efficient photoelectrochemical devices.