The behavior of nickel/YSZ based SOFC anodes after cyclic reduction and oxidation

The reduction and oxidation kinetics of a Ni/yttria stabilized zirconia (YSZ) cermet were studied using thermogravimetric analysis (TGA). It was found that the reduction kinetics were linear. Parabolic kinetics were observed for samples oxidized at low temperatures, but a divergence from parabolic kinetics was observed at oxidation temperatures greater than 700°C.; The volume changes that occurred after cyclic reduction and oxidation were measured using thermomechanical analysis (TMA). Anode substrate samples exhibited no dimensional change after reduction or oxidation at 750°C. Anode functional layer (AFL) samples did not change dimensions during reduction, but expanded by over 2% after oxidation at 750°C.; A baseline of the redox tolerance of an anode supported solid oxide fuel cell (SOFC) was characterized using electron microscopy and electrochemical testing. Cell performance decreased slightly after each redox cycle, especially for redox times greater than two hours. The microstructure of the cell was altered after redox cycling. The results from the baseline redox tests were used to develop four methods to enhance cell redox tolerance.