Oxygen Evolution and Reduction Reactions on La0.8Sr0.2CoO3 (001), (110), and (111) Surfaces in an Alkaline Solution

Abstract

The oxygen evolution and reduction properties of La0.8Sr0.2CoO3 are characterized using two-dimensional model electrodes with different reaction planes, synthesized on SrTiO3 single crystal substrates by pulsed laser deposition. Thin-film X-ray diffraction and reflectivity measurements confirm the epitaxial growth of 29-nm-thick La0.8Sr0.2CoO3 (001), (110), and (111) films on SrTiO3 (001), (110), and (111) substrates, respectively. Cyclic voltammetry curves in 1-M KOH aqueous solution indicate that the (110) film has the highest activity for oxygen evolution and reduction reactions. An expansion of the La0.8Sr0.2CoO3 lattice is observed after the oxygen reduction process, indicating the formation of oxygen defects, with the highest number of defects being produced in the (110) film. X-ray reflectivity analysis demonstrates the formation of a surface layer on the La0.8Sr0.2CoO3 films during electrochemical cycling due to the decomposition of La0.8Sr0.2CoO3. The surface structure constructed at the electrode/electrolyte interface is a crucial factor influencing oxygen evolution and reduction activity of La0.8Sr0.2CoO3.