A Depth‐Resolved In‐Situ Study of the Reduction and Oxidation of Ni‐Based Anodes in Solid Oxide Fuel Cells

The stability of Ni‐YSZ anodes as part of solid oxide fuel cells (SOFCs) towards redox cycling is an important issue for successfully introducing the technology. Detailed knowledge of the NiO‐Ni transitions and their impact on the mechanical integrity of the whole system is necessary to improve the overall stability. In the present paper, a unique in‐situ X‐ray diffraction setup is presented which allows monitoring of the local structural changes during processing of SOFCs. With this setup technological SOFCs – a half cell and a full cell – were studied with respect to NiO‐Ni transitions in repeated reduction‐oxidation cycles, under conditions relevant for SOFC application. It was found that the redox kinetics is a function of the sample depth. Ni particles further away from the surface were reduced/oxidized at a slower rate than particles close to the surface.