Harry Wilson Abernathy

Solid oxide cells often use high-performance (La1−xSrx)(Co1−yFey)O3‑δ (LSCF) air electrodes, but a reaction with the standard YSZ electrolyte creates an insulating layer such as SrZrO3, degrading cell performance. This is typically prevented by adding a dense ceria-based barrier layer between the electrode and electrolyte. However, fabricating this layered structure is a time-consuming, multi-step process. This study introduces a streamlined infiltration-based fabrication method. A porous YSZ backbone is infiltrated with LSCF electrode material and samaria-doped ceria (SDC) as barrier layer. Button cells fabricated via this simplified approach exhibited exceptional durability, maintaining successful operation for 1000 hours under reversible conditions and 500 hours under electrolysis conditions. The demonstrated performance and durability confirm that solution infiltration is an effective manufacturing strategy for integrating SDC barrier layers with LSCF electrodes, suggesting a viable path to reduce solid oxide cell production costs.

In the Ni-based hydrogen electrode of a solid oxide cell (SOC), Ni coarsening is an important degradation mechanism and could be enhanced by NiH diffusing on the Ni particle surfaces. In this work, the average lifetime and diffusion distance of NiH on Ni(111) are computed using density-functional theory and kinetic Monte Carlo methods. It is found that NiH is extremely short-lived and, thus, cannot promote coarsening in the SOC. Also, the diffusion of Ni on Ni(111) is shown to be at most slightly accelerated by H along NiH dissociation paths involving the movement of Ni with a nearby H. Based on this result, coarsening is not likely to be dramatically accelerated by the diffusion of Ni with H on Ni(111). However, support is provided for the experimental procedure of measuring the product of surface coverage and single-species diffusivity of Ni on Ni(111) in a hydrogen-rich atmosphere.

Protonic ceramic fuel cells (PCFCs) offer high energy efficiency at reduced operating temperatures compared to conventional solid oxide fuel cells (SOFCs), but their performance remains limited by sluggish cathodic oxygen reduction reaction (ORR) kinetics. Among potential cathode materials, the BaCo_xFe_yZr_zY_1-x-y-zO_3-δ (BCFZY) perovskite family shows simultaneous conduction of electrons, oxygen ions, and protons and is widely recognized as one of the most promising cathodes for PCFCs because of its outstanding ORR activity and balanced charge transport properties. Although Y doping is known to exert a pronounced influence on the electrochemical performance of BCFZY and has been extensively explored experimentally, the fundamental mechanisms by which it alters intrinsic oxygen transport are still being researched. In this computational study, we examine the effect of Y incorporation on oxygen conductivity in BaFe_0.4Co_0.4Zr_0.2O_3-δ (BCFZ), BaFe_0.4Co_0.4Zr_0.1Y_0.1O_3-δ (BCFZY0.1), and BaFe_0.4Co_0.4Y_0.2O_3-δ (BCFY). Oxygen conductivity was evaluated as the product of tracer diffusivity and oxygen concentration, with diffusivities obtained from ab initio molecular dynamics (AIMD) simulations and oxygen defect concentrations estimated from available reference data. Our findings show that moderate Y doping slightly reduces conductivity from 337 ± 105mS/cm in BCFZ to 203 ± 81mS/cm in BCFZY0.1 at 500 °C, while heavy Y substitution (BCFY) leads to a pronounced reduction to 99 ± 40mS/cm, accompanied by a substantial rise in activation energy from 0.155 ± 0.006 eV and 0.172 ± 0.006 eV to 0.261 ± 0.006 eV. When compared with experimental data (Ref.), the simulated conductivities show more ideal Arrhenius behavior and higher magnitudes than experimental data, indicating that microstructural effects, particularly grain boundaries, play a major role in limiting oxygen transport in real samples. In line with this interpretation, we fixed the bulk conductivity (σ_bulk) to our calculated value and fitted the experimental conductivity (σ_eff), and the grain-boundary conductivity (σ_gb) was then calculated from the series model. (Figure 1) The resulting σ_eff curves matched the experimental trends semi-quantitatively, and the derived σ_gb exhibited grain-boundary behavior typical of oxide conductors. These results clarify how Y doping governs oxygen transport and defect chemistry in BCFZY perovskites, providing insights for optimizing PCFC cathode performance.

Sr-secondary phase formation is a potentially significant degradation mode threatening solid-oxide cell (SOC) commercial viability. A first-principles thermodynamic study was performed for rhombohedral perovskite (La1-xSrx) MnO3±δ (LSM) to assess its stability against Sr secondary phase formation in SOC applications. In this work, the Sr secondary phase formation reaction free energies were determined by combining ab initio lattice dynamics calculations for the solid phases and an ab initio thermodynamics approach for the gas phases. Furthermore, this approach goes beyond previous thermodynamic modeling studies by integrating first-principles based point-defect equilibria into the analyses. The modeling results indicate an increased tendency to form SrO oxide from LSM upon decreasing the oxygen partial pressure. Additionally, enhancing factors to form the Sr-related secondary phase from the associated SrO activity in LSM are further quantified by considering the equilibrium of SrO reacting with contaminant gas species as a function of temperature and gas pressure.

Fuel cells are a vital clean energy technology that converts chemical energy directly into electricity with high efficiency, making them a cornerstone of a sustainable energy future. Herein, we investigate the thermal and chemical lattice expansion behavior of hydrated BaZr_0.78Y_0.22O_3-δ using machine learning-accelerated ab initio molecular dynamics simulations. Our results reproduce the experimentally observed nonmonotonic and anomalous temperature dependence of lattice expansion, which we attribute to the competing effects of thermal expansion and dehydration, two mechanisms that influence the lattice expansion in opposite directions. This work provides fundamental insight into the coupling between hydration thermodynamics and lattice dynamics in BaZr_1-xY_xO_3-δ, a prototypical proton-conducting perovskite, and offers a predictive framework for modeling temperature- and humidity-dependent behavior, critical to solid oxide fuel cell performance.