Proton Shuttles in CeO2/ CeO2-δ Core-Shell Structure

We report a confined proton transportation in a CeO2/CeO2-δ core shell structure to built up proton shuttles, leading to a super proton conductivity of 0.16 S cm-1 for electrolyte and advanced fuel cell performance, 697 mW cm-2 at 520 oC. The isotopic effect provides a direct evidence of proton conduction. The semiconductor nature with the intrinsic CeO2 (i-type) core and n-type CeO2-δ shell reveals special proton transport mechanism. The charged layers are formed at the interface of CeO2-δ/CeO2 heterostructure. There are two factors for proton mobility is limited to the surface of the particles. The first is that the high concentration of oxygen vacancies in the surface layer encourages proton conduction; while the second is that a depletion region created by the core-shell interface inhibits proton migration into the bulk CeO2. Due to the electrostatic repulsion between protons and the positively charged layer, protons’ transportation is constrained at the surface region of the CeO2-δ surface layer. Thu...