Gd3Ga5O12: a wide bandgap semiconductor electrolyte for ceramic fuel cells, effective at temperatures below 500 °C

Abstract

Searching for compatible electrolytes with Ni0.8Co0.15Al0.05LiO2 (NCAL) electrodes with high ionic conductivity at low operational temperatures (<550 °C) is essential for the research on ceramics fuel cells (CFCs). In this work, the experimental and theoretical analyses demonstrate that the highly stable single-phase Gd3Ga5O12 (GGO) garnet structure, composed of Gd-O octahedrons and Ga-O tetrahedrons, provides more active sites for ion transport, resulting in enhanced peak power density (PPD) and stable open circuit voltage (OCV) at low operational temperature. The unique internal garnet structure effectively reduces the interfacial impedance of the prepared fuel cell device, provides many active sites at triple-phase boundaries and increases the electrochemical stability. As a result, the constructed cell can deliver a superior peak power density of 770 mW/cm2 at 490 °C. In addition, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and theoretical calculations further demonstrate electrolyte effectiveness of GGO, enabling stable OCV even at a low temperature of 370 °C under a H2/air environment. This work can help in improving the understanding of the underlying mechanisms of a single-layer fuel cell device, which is essential to further develop this potential energy technology even at a very low temperature of 370 °C.