Impact of nickel on the surface reaction in ceria-based electrodes for solid oxide cells

Nickel/ceria composites as fuel electrodes in solid oxide cells have been in focus of research and development for many years. The mixed ionic electronic conductivity and the electrocatalytic activity of the ceria surface improve performance and durability and enable even single-phase ceria fuel electrodes. Previous studies have shown that the performance of the latter is strongly improved by small amounts of nickel. This raises the question to what extend a single-phase ceria fuel electrode is able to provide a suitable performance during an operation at 600–700 °C and how this is affected by nickel.
In this study, gadolinia doped ceria fuel electrodes, whose surfaces were decorated with different amounts of nickel-nanoparticles, are investigated. The nanoparticles were generated by infiltration of nickel nitrate solutions and subsequent thermal annealing. Impedance spectroscopy, DRT-analysis and a transmission line modeling approach were employed to evaluate the charge transfer resistance of differently decorated ceria surfaces. The analysis revealed a strong impact of nickel on the polarization resistance (f = 30 mHz … 10 kHz) improving from 0.196 Ω⋅cm2 to 0.05 Ω cm2 at 700 °C or more specifically a reduction of the charge transfer resistance at the GDC-surface of up to two orders of magnitude.