Novel functionally graded acicular electrode for solid oxide cells fabricated by the freeze-tape-casting process

The performance of electrode supported solid oxide cells is often limited by gas transport in the thick electrode support. In this study, a novel functionally graded acicular hydrogen electrode microstructure has been fabricated by the freeze-tape-casting method. The effects of freeze-tape-casting processing parameters such as solid loading, freezing bed temperature and tape pulling rate on the morphology of the hydrogen electrode support have been investigated. The electrochemical performance of the cells having the novel functionally graded acicular hydrogen electrode has been significantly improved. In the fuel cell mode, a high power output of 1.28W cm(-2) and a low polarization resistance of 0.166 Omega cm(2) have been achieved at 800 degrees C with H-2 as fuel and ambient air as oxidant using nickel-yttria-stabilized zirconia (YSZ) as the hydrogen electrode, YSZ as the electrolyte, and (La0.75Sr0.25)(0.95)MnO3-YSZ as the oxygen electrode. In the electrolysis mode, a high current density of 2.3 A cm(-2) with 30 vol% absolute humidity in the hydrogen electrode at 800 degrees C has been achieved with an applied cell voltage of 1.6 V. It has been revealed that the novel acicular hydrogen electrode decreases the gas diffusion resistance, thus enhancing the cell performance. (C) 2012 Elsevier B.V. All rights reserved.