Co oxidation state at LSC-YSZ interface in model solid oxide electrochemical cell

Abstract

Oxidation states of cations in a perovskite structure play an important role for conductivity in solid oxide electrochemical cells. For bulk materials oxidation states can be calculated for specific conditions, but is not well understood for micro− /nanostructured materials and at interfaces between materials. We present a fundamental study of interfaces between La 0.6 Sr 0.4 CoO 3-δ (LSC) and yttria-stabilized zirconia (YSZ) in symmetric model solid oxide electrochemical cells. Nanoscale morphology as well as the chemical state of the LSC are investigated by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The experiments were performed in situ at temperatures up to 600 • C in high vacuum (ca. 10 − 7 mbar) and in 2 mbar oxygen. The measured LSC Co oxidation at room temperature is lower than that expected for bulk LSC, indicating a high oxygen vacancy density and possibly high ionic conductivity. However, the Co oxidation state increases with increasing temperature, both in oxygen and in vacuum. The results shows that the Co oxidation state approach that expected for bulk LSC for typical solid oxide fuel or electrolysis cell operation temperatures.

Pathways towards Achieving High Current Density Water Electrolysis: from Material Perspective to System Configuration

“…Meanwhile, SOECs operate at temperatures as high as 1000 °C. Yttria‐stabilized zirconia is a commonly utilized electrolyte material due to its high pure oxygen ion conductivity at temperatures exceeding 800 °C [36,37,46] . But despite its eco‐friendliness and remarkable efficiency, the widespread adoption of this technology has been impeded by several crucial issues such as material and fabrication‐related problems, interlayer diffusion, and poor long‐term cell stability [47] …”