Ultra durable composite steam electrode with cube-shaped BaZr_0.85Y_0.15O_3−δ facet-boosted efficiency toward advanced protonic ceramic electrolysis cells

Protonic ceramic electrolysis cells (PCECs) have attracted significant interest because of their efficiency and environmental sustainability in energy conversion. However, their commercial application is hindered by the absence of effective and robust electrodes capable of operating in harsh environments, such as those characterized by high vapor or CO₂ concentrations. In this study, we developed a stable steam electrode composed of PrBaMn₂O_5+δ (PBM) and the durable proton conductor BaZr_0.85Y_0.15O_3−δ (BZY), which was enhanced with the deposition of PrO_x nano-catalysts. The composite electrode exhibited a low polarization resistance (~0.34 Ω·cm² at 600 °C), comparable to that of conventional cobalt-based electrodes. Additionally, extensive testing over hundreds of hours under severe conditions revealed exceptional durability, with no significant degradation observed. Notably, the electrode composited with cube-shaped BZY microcrystals and PBM showed a higher proton conductivity of 2.15×10⁻⁵ S·cm⁻¹ at 500 °C, representing an entire order of magnitude greater than that of the electrode composited with irregular nanosized BZY. In addition, the single cell achieved a superior electrolysis current of 2.0 A·cm⁻² at 700 °C and 1.3 V. These findings demonstrate the superiority of constructing an innovative interface between the mixed ionic‒electronic conductor (MIEC) and the proton conductor. Our work presents a promising strategy for designing durable steam electrodes for PCECs through a rational compositing approach.