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

Summary 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. Hematite, with the ion transport capacity, is an ideal material to reduce the cost of the solid oxide fuel cell (SOFC). The basic properties of hematite are investigated to determine its potential for low‐temperature SOFC. A composite formed by hematite and Gd0.1Ce0.9O2−δ is developed to promote the performance of the hematite. The composite has even higher ionic conductivity than hematite.