Ultralow Loading of Ru as a Bifunctional Catalyst for the Oxygen Electrode of Solid Oxide Cells

The oxygen evolutionreaction (OER) is a significant contributorto the cell overpotential in solid oxide electrolyzer cells (SOECs).Although noble metals such as Ru and Ir have been utilized as OERcatalysts, their widespread application in SOECs is hindered by theirhigh cost and limited availability. In this study, we present a highlyeffective approach to enhance air electrode performance and durabilityby depositing an ultrathin layer of metallic Ru, as thin as & SIM;7.5 & ANGS;, onto (La0.6Sr0.4)(0.95)Co0.2Fe0.8O3-& delta; (LSCF) usingplasma-enhanced atomic layer deposition (PEALD). Our study suggeststhat the emergence of a perovskite, SrRuO3, resulting fromthe reaction between PEALD-based Ru and surface-segregated Sr species,plays a crucial role in suppressing Sr segregation and maintainingfavorable oxygen desorption kinetics, which ultimately improves theOER durability. Further, the PEALD Ru coating on LSCF also reducesthe resistance to the oxygen reduction reaction (ORR), highlightingthe bifunctional electrocatalytic activities for reversible fuel cells.When the LSCF electrode of a test cell is decorated with & SIM;7.5 & ANGS; of the Ru overcoat, a current density of 656 mA cm(-2) at 1.3 V in electrolysis mode and a peak power density of 803 mWcm(-2) in fuel cell mode are demonstrated at 700 & DEG;C,corresponding to an enhancement of 49.1 and 31.9%, respectively, comparedto the pristine cell.