Preparation and characterization of IrO2–YSZ nanocomposite electrodes by MOCVD

Abstract The electrochemical performance of IrO 2 /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 IrO 2 –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 cm 2 under the experimental conditions (573–873 K). IrO 2 –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. IrO 2 –YSZ films displayed superior electrochemical properties as electrodes to zirconia electrolytes than that exhibited for the Pt–C and conventional Pt paste electrodes.

[1]  B. Steele,et al.  Properties of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) double layer cathodes on gadolinium-doped cerium oxide (CGO) electrolytes. I. Role of SiO2 , 1998 .

[2]  Robert A. Cottis,et al.  Electrochemical impedance and noise , 1999 .

[3]  Young Min Park,et al.  Microstructure and electrical properties of YSZ–NiO composites , 1999 .

[4]  H. B. Wang,et al.  Deposition and characterization of YSZ thin films by aerosol-assisted CVD , 2000 .

[5]  Ž. Skoko,et al.  Thermochemical formation of IrO2 and Ir , 2003 .

[6]  S. H. Kim,et al.  Effects of IrO2/Pt hybrid electrodes on the crystallization and ferroelectric performances of sol-gel-derived Pb(Zr,Ti)O3 thin film capacitors , 2002 .

[7]  Mogens Bjerg Mogensen,et al.  Characterisation of composite SOFC cathodes using electrochemical impedance spectroscopy , 1999 .

[8]  S. Jiang,et al.  Observation of structural change induced by cathodic polarization on (La,Sr)MnO3 electrodes of solid oxide fuel cells , 2003 .

[9]  João A. Labrincha,et al.  Cathode materials for intermediate temperature SOFCs , 2000 .

[10]  M. Mogensen,et al.  Manganite-zirconia composite cathodes for SOFC: Influence of structure and composition , 1995 .

[11]  Paola Costamagna,et al.  Characterisation of composite SOFC cathodes using electrochemical impedance spectroscopy. Analysis of Pt/YSZ and LSM/YSZ electrodes , 2002 .

[12]  Takashi Goto,et al.  Ir–YSZ nano-composite electrodes for oxygen sensors , 2005 .

[13]  M. Mogensen,et al.  Performance/structure correlation for composite SOFC cathodes , 1996 .

[14]  M. Nishiya,et al.  LaMnO3 air cathodes containing ZrO2 electrolyte for high temperature solid oxide fuel cells , 1992 .

[15]  N. Minh.  Ceramic Fuel Cells , 1993 .

[16]  Takashi Goto,et al.  Chemical Vapor Deposition of Iridium, Platinum, Rhodium and Palladium , 2003 .

[17]  M. Dokiya,et al.  Pt-cermet cathode for reduced temperature SOFCs , 2001 .

[18]  Meilin Liu,et al.  Modelling of ambipolar transport properties of composite mixed ionic-electronic conductors , 1996 .