Oxygen diffusion and surface exchange coefficients determined under high pressure: comparisons between oxygen deficient vs. oxygen over-stoichiometric air electrode materials

International audienceMIEC (Mixed Ionic Electronic Conductors) oxides combine, in addition to a high electronic conductivity, high oxygen diffusivity (D) and oxygen surface exchange (k) coefficients. These properties can be directly determined thanks to the so-called IEDP (Isotopic Exchange Depth Profiling) method, which leads to determine the tracer coefficients D* and k*. To date, the reported measurements in the literature have beenperformed at ambient pressure and even below. However, for a higher efficiency of hydrogen production at the system level, or for a ‘Power-to-Gas’ application, it is envisaged to operate the Solid Oxide Electrolysers (SOE) at high pressures, between 10 to 60 bars. In this frame, it becomes mandatory to assess the oxygen reduction/oxidation and the transport properties of the oxygen electrodes materials in the operating conditions, i.e. when there are submitted to such high pressure (HP) at high temperature