In situ redox cycle of a nickel–YSZ fuel cell anode in an environmental transmission electron microscope Original Research Article

Environmental transmission electron microscopy is used in combination with density functional theory calculations to study the redox stability of a nickel/yttria-stabilized zirconia solid oxide fuel cell anode. The results reveal that the transfer of oxygen from NiO to yttria-stabilized zirconia triggers the reduction reaction. During Ni reoxidation, the creation of a porous structure, due to mass transport, accounts for the redox instability of the Ni-based anode. Both the expansion of NiO during a redox cycle and the presence of stress in the yttria-stabilized zirconia grains are observed directly. Besides providing an understanding of the Ni–YSZ anode redox degradation, the observations are used to propose an alternative anode design for improved redox tolerance.