Highly conductive hematite electrolyte for low‐temperature solid oxide fuel cell

Abstract

Hematite (HEM) is a kind of cheap natural mineral with ion transport ability. In this paper, some basic properties of HEM were studied to determine its potential as an electrolyte for low-temperature solid oxide fuel cell (SOFC). A composite (HEM-GDC) formed by Gd0.1Ce0.9O2-δ (GDC) and HEM was developed to improve the performance of the HEM. The result of the X-ray fluorescence spectrometer confirms that the main components of HEM are Fe2O3 and SiO2. The X-ray diffraction (XRD) results show that the chemical compatibilities of HEM and HEM-GDC are good with La2NiO4 + δ (LNO) and NiO-yttria-stabilizedzirconia (NiO-YSZ). Moreover, the thermal expansion coefficients (TECs) of HEM and HEM-GDC are 11.83 × 10−6 K−1 and 12.1 × 10−6 K−1, permitting that they have good physical compatibility with Ni-yttria-stabilized zirconia (Ni-YSZ) and LNO. According to the results of the differential scanning calorimetry with thermal gravimetric analysis (DSC-TGA), HEM and HEM-GDC are stable at high temperatures. The ionic conductivities of HEM and HEM-GDC are 1.07 × 10−2 S·cm−1 and 7.23 × 10−2 S·cm−1 at 450°C, which meet the requirement of the low-temperature SOFC electrolytes. In addition, electrochemical impedance spectra (EIS) tests of GDC, HEM, and HEM-GDC half-cell with LNO as cathode show that HEM-GDC performs best.