SrCe0.9Sm0.1O3-α Compounded with NaCl-KCl as a Composite Electrolyte for Intermediate Temperature Fuel Cell

Abstract

SrCeO₃ and SrCe_0.9Sm_0.1O_3-α were synthesized using a high-temperature solid-state reaction method using Sm₂O₃, SrCO₃, CeO₂ as precursors, then the SrCe_0.9Sm_0.1O_3-α-NaCl-KCl composite electrolyte was fabricated by compounding SrCe_0.9Sm_0.1O_3-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, SrCe_0.9Sm_0.1O_3-α and SrCe_0.9Sm_0.1O_3-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 SrCe_0.9Sm_0.1O_3-α-NaCl-KCl composite electrolyte are four orders of magnitude higher than those of SrCeO₃ and two orders of magnitude higher than those of SrCe_0.9Sm_0.1O_3-α. The result of logσ ~ logpO₂ plot indicates that SrCe_0.9Sm_0.1O_3-α-NaCl-KCl is almost a pure ionic conductor. The electrolyte resistance and the polarization resistance of the H₂/O₂ fuel cell based on SrCe_0.9Sm_0.1O_3-α-NaCl-KCl composite electrolyte under open-circuit condition were 1.0 Ω·cm² and 0.2 Ω·cm² respectively. Further, the obtained maximum power density at 700 °C was 182 mW·cm⁻².