Solid oxide fuel cell Ni-YSZ anodes: Effect of composition on microstructure and performance

Ni-YSZ/YSZ/LSM-YSZ (La0.8Sr0.2MnO3-yttria-stabilized zirconia) solid oxide fuel cells (SOFCs) with varying Ni-YSZ active-layer compositions were compared electrochemically and structurally using a focused ion beam scanning electron microscope. Stereological analyses showed that the highest triple-phase boundary (TPB) density was at a Ni:YSZ volume ratio of similar to 0.5. Although the electrode polarization resistance was minimized at the same composition as the TPB density maximum, the TPB density variation was too small to explain the observed variation in polarization resistance. This implies that polarization resistance was determined not only by TPB density, but also by other structural factors, such as phase tortuosity and contiguity. (C) 2008 The Electrochemical Society.