Electrode polarization measurements in the Fe|SrCe0.95Yb0.05O2.975|Au proton conducting solid electrolyte cell

The effect of hydrogen partial pressure (1.3–5.8 kPa) and cell temperature (600–800 °C) on the kinetics and mechanism of the charge transfer electrode reaction taking place at the three phase boundary H2–Fe–SCY (SCY = SrCe0.95Yb0.05O2.975), was thoroughly examined by performing electrode polarization measurements. A three electrode single chamber proton conducting solid electrolyte cell of the type Fe–SCY–Au, was used in order to conduct the electrode kinetic studies. The steady-state current–overpotential characteristics were analysed with the high field approximations of the Butler–Volmer equation, by taking into account the presence of limiting currents. Both, apparent exchange current density, Io, and anodic/cathodic charge transfer coefficients (αa / αc), were calculated. Limiting currents, Il, were observed in all reaction conditions. The apparent reaction order, q, was found in most cases, within experimental error, close to 0.5 suggesting a possible reaction model, where a competition exists between charge transfer and mass transport of hydrogen ad-atoms or protons along the electrode/solid electrolyte interface.