Defect Chemistry and Transport within Dense BaCe0.7Zr0.1Y0.1Yb0.1O3 − δ(BCZYYb) Proton-Conducting Membranes

This paper uses previously published conductivity measurements as the basis for establishing thermodynamic and transport properties for BaCe0.7Zr0.1Y0.1Yb0.1O3 − δ (BCZYYb) proton-conducting membranes. BCZYYb is mixed ionic-electronic conducting (MIEC) doped perovskite that is dominantly a proton-conducting ceramic. In addition to protons, BCZYYb permits transport of oxygen vacancies and O-site polarons. The present analysis considers the effects of immobile polaron traps. The paper reports enthalpies ΔH° and entropies ΔS° for the defect reactions, and defect diffusion coefficients in Arrhenius form. The paper incorporates the thermodynamic and transport properties into a Nernst–Planck model to characterize BCZYYb performance as a protonic-ceramic membrane for electrolyzer and fuel-cell applications. Especially at temperatures below 600°C, BCZYYb can achieve high faradaic efficiencies (i.e., low electronic leakage) as an electrolyzer membrane.