Stability and functionality of BaCe1-xInxO3-δ as a high temperature proton conducting electrolyte for solid oxide fuel cells

Abstract

Mixed oxides with the perovskite structure are known for their proton conducting ability at the temperatures above 500 °C. This characteristic makes them suitable for application as an electrolyte for intermediate-temperature solid oxide fuel cells. Doping of BaCeO3 with In3+ in place of Ce4+ leads to emergence of oxygen vacancies which take part in creation of proton defects. The characteristics of the BaCe1-xInxO3-δ were investigated in a wide range of In dopant concentrations (x = 0.05; 0.10; 0.15; 0.20; 0.25; 0.30; 0.35 and 0.40). All the samples were synthesized by a citric-nitric autocombustion method. The dense electrolytes were formed after sintering at 1300 °C for 5 h in air. X-ray powder diffraction analysis showed that powders with In content greater than 25 mol% contained In2O3 as a secondary phase. The highest total conductivity around 5×10–3 S•cm–1 was measured for the sample BaCe0.75In0.25O3-δ in the wet hydrogen atmosphere at 700 °C. After exposure to pure CO2 atmosphere at 700 °C for 5 h, the samples were investigated by X-ray diffraction analysis. It was found that even 15 mol% In could completely suppress degradation of the electrolyte. Ni- BaCe0.75In0.25O3-δ/BaCe0.75In0.25O3-δ/LSCF-BaCe0.75In0.25O3-δ fuel cell was tested in wet hydrogen atmosphere and power density output of 264 mW•cm–2 was measured at 700 °C. This result is an indication of stability and functionality of this electrolyte and its versatility in respect to type of fuel and performing environment.