Enhancing Oxygen Evolution Reaction and Stability in Proton-Conducting Solid Oxide Electrolysis Cells (p-SOECs) via a...

Proton-conducting solid oxide electrolysis cells (p-SOECs) offer a promising pathway for intermediate-temperature (400-600 °C) hydrogen production. However, they still face critical challenges related to sluggish oxygen evolution reaction (OER) kinetics and low Faradaic efficiencies. In this work, we demonstrate that introducing a thin (∼0.8 μm) porous Gd_0.1Ce_0.9O_1.95 (GDC) interlayer between a BaCo_0.8Zr_0.1Zn_0.1O_3-δ (BCZZ) oxygen electrode and electrolyte significantly enhances p-SOEC performance. The GDC interlayer reduces polarization resistance by 48% (from 0.54 to 0.28 Ω cm²) and increases Faradaic efficiency from 63% to 81% at -0.8 A/cm² and 600 °C. GDC interlayer p-SOECs display elevated effective H₂ current densities compared to control p-SOECs and reach up to -1.22 A/cm² at 1.3 V. Mechanistic studies on the interactions between GDC and BCZZ reveal that GDC intrinsically promotes OER kinetics by significantly reducing the polarization activation energy (Ea_p), dropping from 1.45 to 1.22 eV for full p-SOECs and from 0.98 to 0.76 eV for symmetric cells. This promotional effect is localized in the electrochemically active region near the electrolyte interface. Durability testing for over 1500 h under 50% H₂O conditions indicates that the GDC interlayer also improves long-term stability, with a degradation rate 53% lower than that of control p-SOECs. By pinpointing the interfacial region where GDC exerts its promotional effect, highlighting its role in enhancing OER kinetics, and establishing interlayer engineering as a powerful technique, this work provides a unified pathway to simultaneously improve p-SOEC activity, Faradaic efficiency, and durability.