Design and Modeling of Proton-Conducting Bilayer Electrolytes Using a Nernst-Planck-Poisson Formulation

Abstract

In this study, the efficiency of proton-conducting ceramic fuel cells was improved by designing bilayer electrolytes with high ion conductivity and low hole conduction. The designs were carried out by finding the thicknesses of anode and cathode-side electrolytes that optimizes efficiency using integral equations based on Wagner theory. Results obtained for bilayer electrolytes were compared with those of single-layer electrolytes. Best performances were found when thin layers of lanthanum tungstate (La28-x W4+x O54+3x/2v2-3x/2) with an La/W ratio of 6.7 (LWO67) were used as cathode-side electrolytes attached to commonly used perovskite materials like BaCe0.9Y0.1O3- δ (BCY10), BaZr0.8Y0.2O3- δ (BZY20), and BaZr0.1Ce0.7Y0.1Yb0.1O3- δ (BZCYYb1711). In addition, the transport properties of a single-layer LWO67 electrolyte were further analyzed by using the Nernst-Planck-Poisson (NPP) model for which parameters were fitted. Finally, a bilayer NPP formulation was explored to obtained the charged defect fluxes and other useful information to enhance the efficiency of a bilayer BZY20|BZCYYb1711 electrolyte.