In situ Studies of Phase Evolution in (Pr_(1-x)Nd_x)_2NiO_4 Electrodes with Various Interlayer Chemistries

摘要

This study is to complement our another paper in this ECS Transactions volume on the role of interlayer on activity and performance stability in praseodymium nickelates. That paper showed a remarkable 48% increase in power density while switching from common GDC interlayer to a new interlayer chemistry (PGCO). Furthermore, a stable long-term performance was linked with suppressed reaction between the cathode and PGCO interlayer. In this paper, we report in situ studies of the phase evolution. The high energy XRD studies at a synchrotron source showed fully suppressed phase transition in praseodymium nickelates with PGCO interlayer, while the electrodes with GDC interlayer undergo substantial phase transformation. Furthermore, in operando and post XRD analyses showed fully suppressed structural changes in electrodes operated in full cells at 750°C and 0.80 V for 500 hours. SEM-EDS analysis showed that the formation of PrO_x at the cathode-interlayer interface may play a role in a decrease of mechanical integrity of the interfaces, due to thermal expansion mismatch, leading to a local stress between the two phases. Consequently, phase evolution at a narrow interface may propagate towards the electrode bulk, leading to structural changes and performance degradation.