Oxygen reduction reaction process of LaNi0.6Fe0.4O3 − δ film - porous Ce0.9Gd0.1O1.95 heterostructure electrode

Relevant factors affecting an oxygen reduction reaction (ORR) in a heterostructure electrode comprising a Ce0.9Gd0.1O1.95 porous layer on LaNi0.6Fe0.4O3 − δ film electrode were evaluated using electrochemical impedance spectroscopy and isotope depth profile analyses. Despite the LaNi0.6Fe0.4O3 − δ film - porous Ce0.9Gd0.1O1.95 electrode having higher interfacial conductivity, σE, compared to a bare LaNi0.6Fe0.4O3 − δ film electrode, σE behavior as a function of p(O2) was similar to each measured temperature. This exhibits a good correlation with the isotopic oxygen depth profile analysis where the evaluated surface oxygen exchange coefficient, k*, showed enhancement compared to bare LaNi0.6Fe0.4O3 − δ film and exhibited the same behavior on p(O2). Based on the analyses, there are two plausible reasons for this enhancement: (a) the formation of triple phase boundaries at the junction of LaNi0.6Fe0.4O3 − δ film, porous Ce0.9Gd0.1O1.95, and gas phase, where the incorporation process during an ORR process takes place via the porous Ce0.9Gd0.1O1.95; and (b) a modification of the subsurface layer just below the film surface where the presence of diffused Ce and Gd appears to accelerate the ORR process.