Stability and spinodal decomposition of the solid-solution phase in the ruthenium–cerium–oxide electro-catalyst

Abstract

The phase diagram of Ru–Ce–O was calculated by a combination of ab initio density functional theory and thermodynamic calculations. The phase diagram indicates that the solubility between ruthenium oxide and cerium oxide is very low at temperatures below 1100 K. Solid solution phases, if existing under normal experimental conditions, are metastable and subject to a quasi-spinodal decomposition to form a mixture of a Ru-rich rutile oxide phase and a Ce-rich fluorite oxide phase. To study the spinodal decomposition of Ru–Ce–O, Ru_0.6Ce_0.4O₂ samples were prepared at 280 °C and 450 °C. XRD and in situ TEM characterization provide proof of the quasi-spinodal decomposition of Ru_0.6Ce_0.4O₂. The present study provides a fundamental reference for the phase design of the Ru–Ce–O electro-catalyst.