Planar proton-conducting ceramic cells for hydrogen extraction: Mechanical properties, electrochemical performance and up-scaling

Proton-conducting ceramics, which selectively separate H₂ from any hydrogen-containing gas could play a role in the future of the growing hydrogen market. In recent years, membrane technologies related to H₂ extraction became attractive solutions to produce pressurized high-purity hydrogen. Yttrium-doped barium zirconate/cerate materials (BaCe_xZr_1-x-yY_yO_3-δ) are among the most studied and used materials. In this study, symmetrical cells consisting of a protonic electrolyte (BaCe_0.2Zr_0.7Y_0.1O_3-δ (BCZY27), 10‒15 μm in thickness) surrounded by two cermet electrodes (BCZY27–Ni (50‒50 vol.%), 150 μm) were prepared for H² extraction applications. The cells were prepared via tape-casting and co-sintered at 1575 °C. The cells were up-scaled to an area of 135 cm². The fracture toughness of the cermet electrodes was determined to be 2.07 (±0.05) MPa∙m^1/2 at room temperature using the double torsion technique. Impedance spectra were recorded on the symmetrical cells between 650 and 800 °C in 3% humidified 50% H₂/50% N₂ atmosphere and at 650 °C varying the hydrogen partial pressure (20% < pH2<100%). In 50% H₂/50% N₂ with 3% H₂O the cells demonstrated an ohmic resistance of 0.59 and 0.44 Ω cm,² an average electrode polarization resistance of 0.10 and 0.09 Ω cm² (per one electrode) at 650 and 800 °C, respectively. Moreover, a stability test was performed over 400 h highlighting the stable electrochemical properties of the symmetrical membranes.