Influence of Polarization on the Morphological Changes of Nickel in Fuel Electrodes of Solid Oxide Cells

Abstract

In this work, morphological changes that patterned nickel films undergo during operations under both solid oxide fuel cell and solid oxide electrolysis modes are investigated using patterned nickel film electrodes. Based on ex situ scanning electron microscope observations, it is found that local morphological changes of nickel at active three-phase-boundaries are influenced by polarization during operations. Under fuel cell mode,the phenomenon of discontinuous nickel spreading caused by the co-effect of enhanced nickel wettability on yttria-stabilized zirconia and nickel coarsening is responsible for the complex morphological changes of patterned nickel film. Under electrolysis mode, the delamination of nickel from the yttria-stabilized zirconia is observed, which is attributed to the weakened nickel wettability on yttria-stabilized zirconia. The phenomena observed during different operations are explained by correlating the nickel wettability on yttria-stabilized zirconia to the level of adsorbed oxygen on the nickel surface, as inferred from the changes in both nickel surface tension and work of adhesion at the nickel-yttria-stabilized zirconia interface.