Chemical stability of BaZr1−xCexO3−δ-based electrolytes in pressurized CO₂

Acceptor doped barium cerates and zirconates are attractive electrolyte materials for use in proton ceramic electrochemical cells. However, the long-term stability of these materials may be compromised by their tendency to react with CO₂. In this work, the chemical stability of the Zr-rich electrolyte materials BaZr0.8Ce0.1Y0.1O3−δ (BZCY81) and BaZr0.9Y0.1O3−δ (BZY10), and the Ce-rich electrolyte materials BaZr0.4Ce0.4Y0.2O3−δ (BZCY442) and BaZr0.4Ce0.4Y0.1Yb0.1O3−δ (BZCYYb4411) are studied in 10 bar CO₂ at 500 °C for 150 h. X-ray diffraction and scanning electron microscopy analysis showed BaCO3 formation for the Ce-rich electrolytes, while the Zr-rich electrolytes showed excellent stability. The chemical stability of the Zr-rich electrolytes was further confirmed under 10% H₂ in CO₂ (10 bar) at 800 °C. Addition of NiO sintering aid to the Ce-rich electrolytes did not have a major impact on the chemical stability although the amount of BaCO3 formation appeared to be slightly reduced.