Comparison of Pr-based Cathodes for IT-SOFCs in the Ruddlesden-Popper Family

摘要

The present study focuses on alternative oxygen electrodes for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs). Among the K_2NiF_4 type compounds, the nickelates Ln_2NiO_(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). Pr_2NiO_(4+δ) shows excellent electrochemical properties and the ageing of the Pr_2NiO_(4+δ)//CGO//8YSZ symmetrical half cells during 1 month under air does not evidence significant change in the R_p value at i_(dc) = 0 condition, despite the decomposition of Pr_2NiO_(4+δ) into the third term of the Ruddlesden-Popper, (R.P.), series (Pr_(n+1)Ni_nO_(3n+1)), Pr_4Ni_3O_(10+δ), the perovskite PrNiO_(3-δ) and Pr_6O_(11). 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 Pr_2NiO_(4+δ), PrNiO_(3-δ) and Pr_4Ni_3O_(10+δ) are thoroughly studied and compared.