NiO/YSZ Reduction for SOFC/SOEC Studied In Situ by Environmental Transmission Electron Microscopy

A typical anode for solid oxide fuel cells (SOFC) or cathode for solid oxide electrolysis cells (SOEC) is a complex porous structure of Ni and yttria-stabilized zirconia (YSZ). The porous Ni/YSZ is usually prepared from powder mixtures of NiO and YSZ, tape casted and sintered into a dense structure and finally reduced during start-up of the SOFC/SOEC in H2 at the operating temperature of the cell (ca. 800 °C). This contribution presents environmental transmission electron microscopy (ETEM) nanoscale observations of the reduction process of a NiO/YSZ powder in H2 at temperatures up to almost 1000 °C. The study focusses on the temperature dependent dynamical morphology of the NiO/YSZ and on the possible influence of YSZ on the NiO reduction.