SrCe0.9Sm0.1O3-α compounded with NaCl-KCl as a composite electrolyte for intermediate temperature fuel cell

Abstract

SrCeO3 and SrCe0.9Sm0.1O3-α were synthesized using a high-temperature solid-state reaction method using Sm2O3, SrCO3, CeO2 as precursors, then the SrCe0.9Sm0.1O3-α-NaCl-KCl composite electrolyte was fabricated by compounding SrCe0.9Sm0.1O3-α with NaCl-KCl and sintering it at a lower temperature (750 °C) than that of a single SrCeO3 material (1540 °C). The phase and microstructure of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The conductivities of the samples were measured in dry nitrogen atmosphere using electrochemical analyzer. The conductivities of the SrCeO3, SrCe0.9Sm0.1O3-α and SrCe0.9Sm0.1O3-α-NaCl-KCl at 700 °C were 2.09 × 10-5 S·cm-1, 1.82 × 10-3 S·cm-1 and 1.43 × 10-1 S·cm-1 respectively. The conductivities of SrCe0.9Sm0.1O3-α-NaCl-KCl composite electrolyte are four orders of magnitude higher than those of SrCeO3 and two orders of magnitude higher than those of SrCe0.9Sm0.1O3-α. The result of logs ~logpO2 plot indicates that SrCe0.9Sm0.1O3-α-NaCl-KCl is almost a pure ionic conductor. The electrolyte resistance and the polarization resistance of the H2/O2 fuel cell based on SrCe0.9Sm0.1O3-α-NaCl-KCl composite electrolyte under open-circuit condition were 1.0Ω·cm2 and 0.2Ω·cm2 respectively. Further, the obtained maximum power density at 700 °C was 182 mW·cm-2.