Influence of architecture for nanostructured Pr 6 O 11 and GDC composite oxygen electrodes on their electrochemical properties and stability
Résumé
The improvement of the electrochemical behavior of solid oxide cells (SOC) strongly
depends on optimizing the oxygen electrode architecture and the choice of electrochemically
active materials. Lanthanide-nickelates are considered as interesting candidates for the active
functional layer in high- to intermediate temperature SOC, however thermally induced cell
deterioration remains a challenge.
Based on decomposition studies of praseodymium-nickelate (Pr2NiO4+δ, PNO) [1], the
electrochemical properties of one of its decomposition products, Pr6O11, were investigated by
Rakesh et al. [2]. For nanostructured Pr6O11 electrodes, deposited by means of electrostatic
spray deposition (ESD) on top of GDC (Ce0.9Gd0.1O2−δ) electrolytes, exceptional low values
of polarization resistance were found (0.02 Ω cm
2
at 600 °C). Combined with the observed
chemical stability (10 days, 800 °C, air), the material was considered a potentially interesting
SOC oxygen electrode material for intermediate temperature application.
The focus of this work was put on the synthesis and electrochemical testing of Pr6O11-GDC
composite electrodes by ESD and screen-printing (SP) with the aim to increase the
electrochemically active interface (triple-phase boundary, TPB) between electrolyte and
electrode material and to support ionic charge transfer. Specifically, the influence of electrode
architecture was investigated by comparing double-layer (Pr6O11 topped by a LSM current
collecting layer (CCL)) and triple-layer architectures (Pr6O11 on porous, screen-printed GDC,
topped by a LSM-CCL), which were prepared based on previous work [3].
In this talk, the impact of ESD parameters and sintering conditions on the Pr6O11 electrode
nanostructure is presented, as well as the importance of a minimum CCL thickness. As a
consequence of different grain sizes and porosity at the Pr6O11-GDC interface, an emphasis is
put on the development of polarization resistance values. Finally, the study of an “ex-situ”
composite triple-layer architecture Pr6O11-GDC cell is discussed.