Infiltrated electrodes for intermediate- network cathode demonstrated a peak power density of
temperature solid oxide fuel cells 0.44 Wcm-2 at 500oC and excellent performance stability.
Fei Zhao1,2, Frank Chen1*, Changrong Xia2
Department of Mechanical Engineering, University of Compared with fuel cells based on protonic conducting
South Carolina, Columbia, SC 29208, USA electrolyte such as polymer electrolyte membrane (PEM)
Laboratory for Renewable Clean Energy, Department of fuel cells, SOFC using oxide ionic conducting electrolyte
Materials Science and Engineering, University of Science has the potential to direct oxidation of hydrocarbon fuels.
and Technology of China, Hefei, 230026 Anhui, China Direct introduction of hydrocarbon fuels requires
reforming and power generation at the anode of the SOFC
Solid oxide fuel cells (SOFCs) are among the most simultaneously. Present development of SOFCs is mainly
promising devices for environmentally clean electricity based on the yttria-stabilised zirconia (YSZ) electrolyte
generation using different fuels such as hydrogen and materials. The most commonly used anode materials for
hydrocarbons. However, SOFCs are currently not YSZ-based SOFCs are Ni/YSZ cermets, which display
economically competitive due to the problems associated excellent catalytic properties for hydrogen oxidation but
mainly with high temperature (>800oC) operation, exhibit limitations such as very low tolerance to sulfur
including degradation of cell components and high cost of and coking when directly operated on hydrocarbon
the interconnect materials.1 Significant efforts thus have fuels.8,9 In this work, infiltration approach has also been
been devoted to lowering the operating temperature for explored to prepare anode with unique material
the development of low temperature SOFCs. At low composition and microstructure in order to suppress
temperature, SOFC resistance increases rapidly and is carbon deposition and improve sulfur tolerance and
often dominated by the interfacial polarization resistance consequently to enhance the cell performance.
between the electrolyte and the cathode. Consequently,
novel electrode materials and/or unique microstructures
have been developed in order to lower the interfacial References:
polarization resistance at low SOFC operating (1) Steele, B. C. H.; Heinzel, A. Nature 2001, 414, 345.
temperatures.2,3 To date, several new electrode (2) Shao, Z. P.; Haile, S. M. Nature 2004, 431, 170.
architectures have been developed to create novel (3 Zhang, Y. L.; Zha, S. W.; Liu, M. L. Adv. Mater. 2005,
structures to achieve high SOFC performances at low 17, 487.
temperatures. Among these, nanostructured electrodes are (4) Sholklapper, T. Z.; Kurokawa, H.; Jacobson, C. P.;
the most attractive since the microstructures in nanometer Visco, S. J.; De Jonghe, L. C. Nano Lett. 2007, 7, 2136.
scale will make available larger tri-phase boundaries (5) Jiang, S. P. Mater. Sci. & Eng. A 2006, 418, 199.
(TPBs) for the electrocatalytic processes of oxygen (6) Huang, Y. Y.; Ahn, K.; Vohs, J. M.; Gorte, R. J. J.
reduction. The nanostructured electrodes are typically Electrochem. Soc. 2004, 151, A1592.
formed by incorporating nanoparticles to preformed (7) Zhao, F.; Peng, R. R.; Xia, C. R. Mater. Res. Bull.
porous electrode frame with an ion-impregnation process 2008, 43, 370.
involving adsorption and subsequent decomposition of (8) Matsuzaki, Y.; Yasuda, I. Solid State Ionics 2000,
metal salts.4-7 This process usually generates 25-300 nm 132, 261.
granular particulates randomly located on the inner (9) McIntosh, S.; Gorte, R. J. Chem. Rev. 2004, 104,
surfaces of the frame.5 The nanoscale granular particles 4845.
are believed to be the primary reason for the high SOFC
In this work, infiltration approach has been explored to
make cathode with unique microstructure which has
shown improved cell performance. For example, nano-
network of typical cathode material, Sm0.5Sr0.5CoO3−δ
(SSC), has been formed through infiltration approach for
low-temperature SOFC applications. The nano-network,
as shown in Figure 1, is consisted of well-connected SSC
nanowires, forming straight conducting path for oxygen-
ion and electron conduction. The nano-network formation
mechanism will be discussed. In addition, the nano-
network has high porosity and the SSC nanowires are
composed of SSC nanobeads. Such a cathode
microsturcture shows extremely high cathode
performance. An anode supported cell with the nano-
Figure 1. Cross-sectional microstructure for
infiltrated SSC cathode