Fast ionic conduction and rectification effect of NaCo0.5Fe0.5O2-CeO2 nanoscale heterostructure for LT-SOFC electrolyte application

Heterostructure electrolytes made of semiconductor and ionic conductor have drawn significant attention in solid oxide fuel cells (SOFCs) field owing to their attractive ionic conductivity at low operating temperatures. In this study, a new heterostructure is proposed by introducing a layered semiconductor NaCo0.5Fe0.5O2 (NCF) into fluorite structure ionic oxide CeO2 for SOFC electrolyte uses. The prepared samples are characterized in views of phase structure, surface and interface property, and electrical conductivity, followed by being applied in SOFCs for performance, impedance spectra and durability assessment. It is found the NCF-CeO2 forms nanoscale heterostructure with massive hetero-interfaces and enriched oxygen vacancies. The best-performing sample 35NCF-65CeO(2) gains improved ionic conduction and promising SOFC performance with power density of 68-1010 mW cm(-2) at 350-550 degrees C. Moreover, durability measurement verifies the NCF-CeO2 based SOFC can be stably operated for 160 h under fixed current density of 100 mA cm(-2), whereas there is an obvious degradation in the initial 5 h. A particular attention is paid to investigate the dynamic electrochemical process and junction rectification effect of the NCF-CeO2 cell to interpret the degradation behaviour. Our findings thus certify the great promise of layered and fluorite oxide based NCF-CeO2 nanoscale heterostructure for low-temperature SOFC electrolyte uses. (c) 2022 Elsevier B.V. All rights reserved.