Proton Conduction and Fuel Cell Using the CuFe-Oxide Mineral Composite Based on CuFeO2 Structure

Abstract

High ionic conductivity has attracted considerable attention for use in energy applications, such as solid oxide fuel cells (SOFCs). Novel proton conductivity was discovered in a delafossite-based CuFe-oxide composite from a natural mineral. Low-temperature (400–550 °C) SOFCs (LTSOFCs) using the natural CuFe-oxide composite as an electrolyte were demonstrated. Power densities of 775 mW cm–2 were achieved at 550 °C for the CuFeO2 electrolyte, 423 mW cm–2 for the CuFe-oxide from the natural mineral, and 672 mW cm–2 by further introducing proton-dominating conduction into the CuFe-oxide natural material. We found that the CuFeO2 delafossite structure played a key role in high ionic conductivity. Theoretical calculations indicated that enhanced proton transport through the Cu–O layer was associated with a low activation energy (0.23–0.26 eV) and rapid transport kinetics, which were consistent with the experimental results. Both theoretical and experimental results demonstrated that the CuFeO2 delafossite mate...