An Unbalanced Battle in Excellence: Revealing Effect of Ni/Co Occupancy on Water Splitting and Oxygen Reduction Reactions in Triple-Conducting Oxides for Protonic Ceramic Electrochemical Cells.

Porous electrodes that conduct electrons, protons, and oxygen ions with dramatically expanded catalytic active sites can replace conventional electrodes with sluggish kinetics in protonic ceramic electrochemical cells. In this work, a strategy is utilized to promote triple conduction by facilitating proton conduction in praseodymium cobaltite perovskite through engineering non-equivalent B-site Ni/Co occupancy. Surface infrared spectroscopy is used to study the dehydration behavior, which proves the existence of protons in the perovskite lattice. The proton mobility and proton stability are investigated by hydrogen/deuterium (H/D) isotope exchange and temperature-programmed desorption. It is observed that the increased nickel replacement on the B-site has a positive impact on proton defect stability, catalytic activity, and electrochemical performance. This doping strategy is demonstrated to be a promising pathway to increase catalytic activity toward the oxygen reduction and water splitting reactions. The chosen PrNi0.7 Co0.3 O3- δ oxygen electrode demonstrates excellent full-cell performance with high electrolysis current density of -1.48 A cm-2 at 1.3 V and a peak fuel-cell power density of 0.95 W cm-2 at 600 °C and also enables lower-temperature operations down to 350 °C, and superior long-term durability.

Root Cause Analysis of Degradation in Protonic Ceramic Electrochemical Cell with Interfacial Electrical Sensors Using Data-Driven Machine Learning.

Protonic ceramic electrochemical cells (PCECs) offer promising paths for energy storage and conversion. Despite considerable achievements made, PCECs still face challenges such as physiochemical compatibility between componenets and suboptimal solid-solid contact at the interfaces between the electrolytes and electrodes. In this study, a novel approach is proposed that combines in situ electrochemical characterization of interfacial electrical sensor embedded PCECs and machine learning to quantify the contributions of different cell components to total degradation, as well as to predict the remaining useful life. The experimental results suggest that the overpotential induced by the oxygen electrode is 48% less than that of oxygen electrode/electrolyte interfacial contact for up to 1171 h. The data-driven machine learning simulation predicts the RUL of up to 2132 h. The root cause of degradation is overpotential increase induced by oxygen electrode, which accounts for 82.9% of total cell degradation. The success of the failure diagnostic model is demonstrated by its consistency with degradation modes that do not manifest in electrolysis fade during early real operations. This synergistic approach provides valuable insights into practical failure diagnosis of PCECs and has the potential to revolutionize their development by enabling improved performance prediction and material selection for enhanced durability and efficiency.

Mathematical Model-Assisted Ultrasonic Spray Coating for Scalable Production of Large-Sized Solid Oxide Electrochemical Cells.

Thin solid oxide films are crucial for developing high-performance solid oxide-based electrochemical devices aimed at decarbonizing the global energy system. Among various methods, ultrasonic spray coating (USC) can provide the throughput, scalability, quality consistency, roll-to-roll compatibility, and low material waste necessary for scalable production of large-sized solid oxide electrochemical cells. However, due to the large number of USC parameters, systematic parameter optimization is required to ensure optimal settings. However, the optimizations in previous literature are either not discussed or not systematic, facile, and practical for scalable production of thin oxide films. In this regard, we propose an USC optimization process assisted with mathematical models. Using this method, we obtained optimal settings for producing high-quality, uniform 4 × 4 cm2 oxygen electrode films with a consistent thickness of ∼27 µm in 1 min in a facile and systematic way. The quality of the films is evaluated at both micrometer and centimeter scales and meets desirable thickness and uniformity criteria. To validate the performance of USC-fabricated electrolytes and oxygen electrodes, we employ protonic ceramic electrochemical cells, which achieve a peak power density of 0.88 W cm-2 in the fuel cell mode and a current density of 1.36 A cm-2 at 1.3 V in the electrolysis mode, with minimal degradation over a period of 200 h. These results demonstrate the potential of USC as a promising technology for scalable production of large-sized solid oxide electrochemical cells.