Polarization study of Fe|BaCe0.5Zr0.3Y0.08Yb0.08Cu0.04O3-δ|Fe electrochemical cells in wet H2 atmosphere

Abstract

In the present work, the steady-state current-overpotential characteristics of the Fe|BaCe0.5Zr0.3Y0.08Yb0.08Cu0.04O3-δ|Fe interface as a function of the gas phase composition and temperature are investigated. To this purpose a BaCe0.5Zr0.3Y0.08Yb0.08Cu0.04O3–δ dense ceramic material is successfully synthesized by solid state synthesis and sintered at 1400 °C. Then its crystal structure, ceramic and electrical properties are investigated. It is found that the ceramic has a high relative density (more than 90%) and acceptable proton conductivity (1.5 and 6.8 mS cm−1 at 500 and 900 °C, respectively). On the as prepared BaCe0.5Zr0.3Y0.08Yb0.08Cu0.04O3–δ electrolyte disk, three thin Fe porous layers are deposited by painting on both sides (three electrode system), which is then immersed in a tubular single-chamber continuous electrochemical reactor.The polarization measurements are carried out in the temperature range between 500 and 700 °C and at three different H2/He wet (3% steam) compositions. The apparent anodic and cathodic charge transfer coefficients (Tafel region) are found to be: αa = αc = 0.8, while the apparent activation energy is calculated to be approximately 0.55 ± 0.05 eV. It is also found that by increasing the hydrogen concentration the current density increases, especially at higher temperature values.