Optimization of anode structure for intermediate temperature solid oxide fuel cell via phase-inversion cotape casting

A functional layer and a porous support that together constitute an anode for a solid oxide fuel cell were simultaneously formed by the phase-inversion tape casting method. Two slurries, one composed of NiO and yttria-stabilized zirconia (YSZ) powders and the other of NiO, YSZ, and graphite were cocasted and solidified by immersion in a water bath via the phase-inversion mechanism. The as-formed green tape consisted of a sponge-like thin layer and a fingerlike thick porous layer, derived from the first slurry and the second slurry, respectively. The former acted as the anode functional layer (AFL), while the latter was used as the anode substrate. The AFL thickness was varied between 20 and 60 lm by adjusting the blade gap for the tape casting. Single cells based on such NiO-YSZ anodes were prepared with thin YSZ electrolytes and YSZ-(La0.8Sr0.2)(0.95)MnO3-delta (LSM) cathodes, and their electrochemical performance was measured using air as oxidant and hydrogen as fuel. The maximum power densities obtained at 750 degrees C were 720, 821, and 988 mW cm(-2) with the AFL thickness at 60, 40, and 20 lm, respectively. The satisfactory electrochemical performance was attributed to the dual-layer structure of the anode, where the sponge-like AFL layer provided plenty of triple-phase boundaries for hydrogen oxidation, and the fingerlike thick porous substrate allowed for facile fuel transport. The phase-inversion tape casting developed in this study is applicable to the preparation of other planar ceramic electrodes with dual-layer asymmetric structure.