Aurélien Flura

Decomposition of the layered Ruddlesden–Popper (RP) phase Pr₂NiO_4+δ into higher order phases during long-term annealing dramatically enhances oxygen transport.

The present study focuses on alternative oxygen electrodes for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs). Among the K₂NiF₄ type compounds, the nickelates Ln₂NiO_4+δ (Ln = La, Pr or Nd) have already shown their suitability as oxygen electrode due to their mixed ionic and electronic conductivity (i.e. MIEC properties). Pr₂NiO_4+δ shows excellent electrochemical properties and the ageing of the Pr₂NiO_4+δ//CGO//8YSZ symmetrical half cells during 1 month under air does not evidence significant change in the R_p valueat i_dc = 0 condition, despite the decomposition of Pr₂NiO_4+δ into the third term of the Ruddlesden-Popper, (R.P.), series (Pr_n+1Ni_nO_3n+1), Pr₄Ni₃O_10+δ, the perovskite PrNiO_3-δ and Pr₆O₁₁. Such decomposition is also observed after one month at different SOFC operating temperatures, namely 600, 700 and 800 °C under air. Aiming at further understanding, the relationship between the electrochemical behavior and the phase stability, the physico-chemical and electrochemical properties of Pr₂NiO_4+δ, PrNiO_3-δ and Pr₄Ni₃O_10+δ are thoroughly studied and compared.