Study on new BaCe0.7In0.3O3−δ-Gd0.1Ce0.9O2−δ composite electrolytes for intermediate-temperature solid oxide fuel cells

New mixed ionic conductors, BaCe0.7In0.3O3−δ-Gd0.1Ce0.9O2−δ (BCI-GDC, weight ratio, 3:7, 5:5 and 7:3), were synthesized via a one-step citric acid-nitrate gel combustion method as electrolyte materials for solid oxide fuel cells (SOFCs). X-ray diffraction patterns of BCI-GDC indicated that there was no impurity phase formed after sintering at high temperature up to 1400 °C. Scanning electron microscopic study of BCI-GDC depicted dense grain morphology. Single fuel cells were prepared and the corresponding electrochemical performances were tested. The sintering temperature of the dense composite electrolyte membranes decrease as the BCI content increases because of the sintering aids of In element. All samples with the composite electrolyte showed higher open circuit voltage (OCV) values than the single phase GDC. In addition, Electrical conductivity of the composite electrolyte under different atmospheres at different temperatures confirmed that the BCI-GDC exhibited high mixed oxygen ionic and protonic conduction. The test results indicated that the conductivity and OCV values of the composite electrolyte enhanced as the GDC content increases, and the optimum performance was found to be BCI3-GDC7 compared with the pure BCI and GDC electrolyte. The possible interface effects were suggested to explain this phenomenon. Our results not only provide one new promising composite electrolyte material for intermediate-temperature SOFCs but the composition dependence can actually provide a guide for the material design, optimization.