Microstructural analysis of a solid oxide fuel cell anode using focused ion beam techniques coupled with electrochemical simulation

Porous composite electrodes play a critical role in determining the performance and durability of solid oxide fuel cells, which are now emerging as a high efficiency, low emission energy conversion technology for a wide range of applications. In this paper we present work to combine experimental electrochemical and microstructural characterisation with electrochemical simulation to characterise a porous solid oxide fuel cell anode. Using a standard, electrolyte supported, screen printed Ni-YSZ anode, electrochemical impedance spectroscopy has been conducted in a symmetrical cell configuration. The electrode microstructure has been characterised using FIB tomography and the resulting microstructure has been used as the basis for electrochemical simulation. The outputs from this simulation have in turn been compared to the results of the electrochemical experiments. A sample of an SOFC anode of 6.68 mu m x 5.04 mu m x 1.50 mu m in size was imaged in three dimensions using FIB tomography and the total triple phase boundary density was found to be 13 mu m(-2). The extracted length-specific exchange current for hydrogen oxidation (97% H-2, 3% H2O) at a Ni-YSZ anode was found to be 0.94 x 10(-10), 2.14 x 10(-10), and 12.2 x 10(-10) A mu m(-1) at 800, 900 and 1000 degrees C, respectively, consistent with equivalent literature data for length-specific exchange currents for hydrogen at geometrically defined nickel electrodes on YSZ electrolytes. (C) 2010 Elsevier B.V. All rights reserved.