(Invited) High Performing and Stable Proton-Conducting Solid Oxide Electrolysis Cells with Triple Conducting Anodes

Abstract

Proton-conductors BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) and La2Ce2O7 (LDC) are combined to create an interface active and steam-tolerant electrolyte for high-performance proton-conducting solid oxide electrolysis cells. LDC shows good chemical compatibility with BZCYYb. The readily fabricated LDC/BZCYYb bilayer electrolyte can be densified at a temperature as low as 1300oC vs. ~1600oC for the benchmark vapor-stable BaZr0.8Y0.2O3-δ electrolyte. With Pr2NiO4+δ as the anode and Ni as the cathode catalyst, this bilayer electrolyte cell yields a current density of 975 mA/cm2 and 300 mA/cm2 under a 1.3 V applied potential at 700oC and 600oC, respectively. This performance is among the best of all H-SOECs equipped with a chemically stable electrolyte so far. BZCYYb layer in the bilayer electrolyte promotes the hydrogen evaluation reaction at the cathode side, resulting in a 108% improvement over the cell without this layer. The LDC layer, on the other hand, effectively protects this functional BZCYYb layer from high concentration of vapor in a practical SOEC operation condition. The cell without LDC layer shows degradation in terms of increase in the electrolyzing potential from 1.07 V to 1.29 V during a 400 mA/cm2 operation at 700oC. In contrast, the bilayer electrolyte cell maintains the same electrolyzing potential of 1.13 V under the same conduction for a 102 h operation. These findings demonstrate that this synergic bilayer electrolyte design could be a vital strategy to overcome the dilemma between performance and stability faced by the current benchmark Zr- or Ce-rich Ba(CeZr)O3-δ electrolytes, achieving good performance and stability at the same time.