PNNL

Abstract

Determining the role of lattice oxygen in the oxygen evolution reaction (OER) is pivotal to understanding reaction mechanisms and predictive design of electrocatalysts based on transition metal oxides. Here, using well-defined, isotope (18O)-enriched, epitaxial LaNiO3 thin films as a model system, we show that dynamic lattice oxygen exchange occurs during OER. Time-of-flight secondary ion mass spectrometry studies reveal that lattice oxygen exchange can affect the top 2 nm of the LaNiO3 films, but the surface remains crystalline and in the perovskite phase after OER. In addition, cyclic voltammetry and potentiostatic measurements show that OER kinetics are strongly pH dependent, which is different from what is expected from the typical four concerted proton-electron transfer steps, most likely due to the involvement of lattice oxygen. Our findings suggest that the roles of lattice oxygen during OER, and charge transfer mechanisms in such systems, need to be further studied in order to design more efficient and stable electrocatalysts.