Overcoming Chromium Poisoning in Solid Oxide Cells Through Multiscale Perovskite Engineering

Abstract Chromium (Cr) poisoning and sluggish oxygen kinetics remain critical challenges for reversible solid-oxide-cell (RSOC) oxygen electrodes. We report a triple-barrier strategy that integrates lattice stabilization through Ba-induced suppression of SrO segregation, exsolved BaCoO₃ nano-domains for Cr trapping, and surface acidity regulation via trace Mo doping at the B-site within La0.6Sr0.1Ba0.35Co0.2Fe0.78Mo0.02O₃₋δ. The resulting electrode exhibits a polarization resistance of 0.058 Ω·cm² at 750°C (70.4% reduction versus LSCF) and an oxygen surface-exchange coefficient of 2.01×10⁻³ cm·s⁻¹. Single cells achieve 1.352 W·cm⁻² at 800°C in fuel cell mode and 2.08 A·cm⁻² at 1.5 V in electrolysis mode. Under 0.5 A·cm⁻² current density with Cr₂O₃ exposure, the cell maintains stable performance for approximately 1000 h. Electrochemical impedance spectroscopy with distribution of relaxation times analysis, CO₂/NH₃ temperature-programmed desorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary-ion mass spectrometry reveal suppressed SrCrO₄ formation and reduced Cr ingress, consistent with BaCoO₃-mediated trapping and Mo-controlled surface acidity. Density functional theory calculations demonstrate that Ba/Mo co-doping weakens CrO₃ adsorption at La–O–Sr sites by reducing local electron density. This design reconciles high activity with Cr tolerance under RSOC-relevant conditions and provides transferable principles for oxygen-electrode development.