Sol–gel processing of IrO2–TiO2 mixed metal oxides based on an iridium acetate precursor

Mixed IrO2–TiO2 oxides were prepared by the sol–gel method by adding an aqueous solution of an iridium(III) acetate precursor [Ir3O(OAc)6 (HOAc)3]OAc, to titanium tetraethoxide in ethanol. By using an acetylacetonate modifier to stabilize the hydrolysed titanium alkoxide and by omitting a catalyst, gels were produced in all cases. Transmission electron microscopy and EDX analysis confirmed the high dispersion of iridium in the dried gel material on the nanometre scale. The images also show spherical cage features up to 20 nm in diameter. High mass losses of the gels in the TGA scans suggested low degrees of hydrolysis of the acetate precursor, but calcination gave a crystalline, mixed oxide (TixIr1–xO2) solid solution. The precursor is also soluble in ethanol, which provides a slightly modified route to similar materials.