Preparation and characterization of IrO2–YSZ nanocomposite electrodes by MOCVD

The electrochemical performance of IrO2/yttria stabilized zirconia (YSZ) cermet cathodes for solid oxide fuel cells was experimentally evaluated in relation to their microstructure. Noble metal films were prepared by MOCVD using metal–acetylacetonate precursors which were mixed and evaporated together (493 K) to achieve codeposition. The effects of experimental conditions on deposition rates, composition and microstructure were studied, and the optimum conditions were determined. The growth of the films was columnar and layered in structure, with porous morphology. TEM observations revealed that the IrO2–YSZ composites are constituted by single-phase particles, between 4 and 10 nm in size, with an excellent composite distribution. The cathode-related polarization resistance, Rp, was measured by impedance spectroscopy and found to be in the range of 21–968 Ω cm2 under the experimental conditions (573–873 K). IrO2–YSZ electrodes undergo structural and/or morphological changes caused by cathodic polarization and high temperature (873 K). However, this behavior could contribute to the improvement of the electrochemical performance of the electrode. IrO2–YSZ films displayed superior electrochemical properties as electrodes to zirconia electrolytes than that exhibited for the Pt–C and conventional Pt paste electrodes.