Proton Transport Along Fluorite Oxide-Ion Conductor: Unveiling Abnormally High Conduction Characteristics and Synergistic Mechanisms

Abstract

Abstract Common perovskite oxide electrolytes, such as BaCe(Zr)O3−δ, exhibit proton conductivity ranging from 10− 3 to 10− 2 S cm− 1 at 600°C for protonic ceramic fuel cells (PCFCs). This study presents a novel approach to develop high proton conduction along oxide-ion conductor of a fluorite gadolinium doped ceria (GDC: Gd0.1Ce0.9O2−δ) by electrochemical proton injection via an in-situ fuel cell process. A high ionic conductivity of 0.17 S cm− 1 has been achieved and a fuel cell employing a 400-µm thick GDC electrolyte delivered a peak power output close to 1000 mW cm− 2 at 500°C, validating the effectiveness of proton conduction. The transformation process of GDC from an oxygen-ion conductor to a proton conductor revealed a synergistic mechanism involving both surface proton conduction and bulk oxygen-ion migration. These findings provide new insights into the ionic transport mechanism and offer opening new avenues for advanced protonic ceramic fuel cells at lower temperatures.