Sr1−Ca MoO3–Gd0.2Ce0.8O1.9 as the anode in solid oxide fuel cells: Effects of Mo precipitation

Abstract

Abstract Calcium is incorporated into strontium molybdate to form Sr 1 − x Ca x MoO 3 as an electronic conductor for solid oxide fuel cells (SOFCs). Metallic molybdenum was observed with the increasing content of Ca substitution for Sr in Sr 1− x Ca x MoO 3 . Rietveld refinement reveals the phase transition from cubic to tetragonal perovskite structure, which implies its decreased thermodynamic stability under reducing conditions with increasing content of Ca. X-ray diffraction (XRD) and differential scanning calorimetry-thermo-gravimetric analysis (DSC-TGA) further prove that this Mo ex-solution is reversible. The electrochemical performances of Sr 1− x Ca x MoO 3 towards H 2 and CH 4 oxidation at 800 °C are examined. The performance is improved in H 2 atmosphere with the introduction of Ca, 330 mW cm −2 of Sr 0.5 Ca 0.5 MoO 3 –Gd 0.2 Ce 0.8 O 1.9 (GDC) vs. 280 mW cm −2 of SrMoO 3 –GDC, which can be ascribed to the segregated Mo as the additional catalyst. However, carbon deposition is observed after exposure to CH 4 at 800 °C for both Sr 0.7 Ca 0.3 MoO 3 –GDC and Sr 0.5 Ca 0.5 MoO 3 –GDC, in contrast to the absence of carbon on SrMoO 3 –GDC.