Pr and Ti co-doped Strontium Ferrite as a Novel Hydrogen Electrode for Solid Oxide Electrolysis Cell

Pr and Ti co-doped strontium ferrite oxide Pr_0.3Sr_0.7Ti_0.3Fe_0.7O_3−δ (PSTF) has been examined as a hydrogen electrode for solid oxide electrolysis cell (SOEC). X-ray diffraction analysis shows that the PSTF material maintains phase stability during 20 hours of treatment under 5%H₂/N₂ conditions. An SOEC with a configuration of PSTF||SDC|YSZ||LSM-YSZ operates under various H₂O concentrations and current densities. As can be observed from the AC impendence spectra of the PSTF electrode, H₂O/H₂ adsorption desorption or surface diffusion process is the main rate-limiting step for steam electrolysis reaction. The low-frequency arc R_L obviously depends on the H₂O concentration and the electrolysis current density. Steam starvation in hydrogen electrode occurs at low H₂O concentration and large current density. A maximum current density of 302 mA cm⁻² is obtained at an electrolysis voltage of 1.46 V in Ar/H₂/60%H₂O at 800 °C. The corresponding polarization resistance of PSTF electrode is as small as 0.25 Ω cm². This study demonstrates that Pr_0.3Sr_0.7Ti_0.3Fe_0.7O_3−δ is a promising hydrogen electrode material of SOEC for H₂O electrolysis.