Dye-sensitized nanostructured crystalline mesoporous tin-doped indium oxide films with tunable thickness for photoelectrochemical applications

摘要

A simple route towards synthesis of nanostructured mesoporous Indium-Tin Oxide (templatednano-ITO) electrodes exhibiting both high conductivities and optimized bicontinuous pore-soiid 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 coating$ with the cubic bixbyite structure. In particular, 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'-(CH2PO3H2)2-bpy)]Cl2 1 (bpy = bipyridine). Surface coverage was shown to increase with the film thickness, from 0.7 x 10~(-9) molcm~(-2) (one layer, 45 nm) to 3.5 x 10~(-9) molcm~(-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.