The rutile metal oxides IrO2 and RuO2 are highly active for the oxygen evolution reaction (OER). Perovskite oxides containing the same transition metals (SrIrO3, SrRuO3) have notably lower overpotentials, but decreased stability. For strontium ruthenate (SRO) in alkaline media, oxygen is evolved at potentials just greater than the thermodynamic potential of OER, but commensurate with decomposition of the perovskite lattice and subsequent loss of activity. In contrast, manganese oxides, such as the perovskite La0.70Sr0.30MnO3 (LSMO), are relatively stable in OER environments but are also less active. We studied a series of thicknesses of LSMO (0 – 70 unit cells, up to ~27 nm) grown epitaxially atop SRO to investigate the relationship between activity and stability under OER conditions in alkaline electrolyte. We compare the enhanced activity (yet decreased stability) for intermediate thicknesses of LSMO atop SRO to films of comparable thickness without the underlying SRO layer to deconvolute thickness effects from emergent phenomena. A fast redox couple was employed to understand the charge transfer dynamics, and we further consider the oxidative behavior in the presence of Cl- salts to probe competitive adsorption, oxidation, and potential corrosion effects, as ruthenium oxides are typically highly active for the chlorine evolution reaction as well. The findings from this systematic study of protective oxide coatings will enable the design of catalyst heterostructures with desired activity and stability.

Tailoring activity and stability of oxygen evolution catalysts with perovskite oxide coatings

ACS Spring Meeting 2021

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