Operando Characterizations of Proton Exchange in Proton Conducting Solid Oxide Electrolysis Cells (p-SOECs)

The proton conducting solid oxide electrolysis cell (p-SOEC) has attracted tremendous attention for its fast hydrogen production at intermediate temperatures. This work characterizes transport and hydration properties of the state-of-the-art electrolyte materials using in situ Diffuse reflectance infrared Fourier transform infrared spectroscopy (DRIFTS) together with electrochemical impedance spectroscopy (EIS). The adsorption of water molecules and formation of surface hydroxyl groups on the electrolyte surface as a function of temperature, steam concentration, and electrical potential were systematically investigated by DRIFTS under operando conditions. The quantitative information on the concentration of hydroxyl species on the electrolyte materials before and after exposure to steam were obtained. The determination of OH intensity leads to the direct determination of the proton exchange coefficient k, at different steam concentrations and biases. Thermalgravimetric analysis (TGA) was used to reveal bulk hydration behaviors. The results are unique and should be able to provide valuable insights into the mechanisms of proton formation, migration, and evolution under various operating conditions, which is critical to design better electrolyte compositions and optimize the operation conditions for next-generation p-SOECs.