Proton Shuttles in CeO2/CeO2−δ Core–Shell Structure
A core-shell structure with a CeO2 core and a non-stoichiometry CeO2-d surface layer built up proton shuttles, leading to a super proton conductivity of 0.15 S cm-1 and advanced fuel cell performance, 661 mW cm-2 at 520 ºC. The surface induced conduction process was investigated through a heat-treatment procedure for CeO2 pellets at different temperatures. The surface layer was observed to experience ordering and disappearing after high temperature treatments. Proton conduction was verified via electrochemical impedance spectra, proton conducting isotopic effect and fuel cell measurement. The isotopic effect provided a direct evidence on proton conduction and proton conduction mechanism was further investigated based on the semiconductor nature with the intrinsic CeO2 (i-type) core and n-type CeO2-δ shell. The charged layers were formed at the interface of CeO2-δ/CeO2 core-shell heterostructure with a positively charged layer located at CeO2-δ side of the interface and negative charged layer located at the intrinsic CeO2. Due to the electrostatic repulsion between protons and the positively charged layer, protons’ transportation is limited at the surface region of the CeO2-δ shell. Thus, continuous “proton shuttles” are formed, resulting in super conductivity. This work presents a new methodology and scientific understanding for fast proton transport in general oxides and advanced proton ceramic fuel cells (PCFCs).
National Natural Science Foundation of China (NSFC; Grant Nos. 51772080, 51774259, and 51672208).
- Aeronautical, Automotive, Chemical and Materials Engineering
- Aeronautical and Automotive Engineering