Enhancing Ni-YSZ Anode Resilience to Environmental Redox Stress with Aluminum Titanate Secondary Phases

Abstract

Voltammetry, impedance spectroscopy, and operando vibrational Raman spectroscopy were used to examine the resilience of traditional and modified Ni-based SOFC anodes to environmental reduction/oxidation (redox) cycling. Traditional anodes were fabricated from Ni yttrium stabilized zirconia (YSZ) cermets while modified anodes consisted of the Ni-YSZ cermet containing 4 wt % Al2TiO5 (ALT). Anodes were part of full membrane electrode assemblies that included a YSZ electrolyte support and a LSM cathode. Experiments were performed at 800 °C. To examine anode resilience to redox cycling, cells operated with hydrogen under galvanostatic conditions for 20 min prior to oxidation at OCV using either H2O or O2. While H2O only partially oxidized anodes, O2 exposure fully oxidized anodes and rapidly accelerated degradation in undoped cells. Undoped cells typically suffered a 50% loss in conversion efficiency after approximately 15–20 redox cycles with O2. Under equivalent conditions, cells with ALT doped anodes degraded on average only 13 ± 3%. EIS modeling and ex situ FE-SEM measurements provide further insight into the mechanisms responsible for enhanced resilience shown by Ni-YSZ cermet anodes doped with ALT.