Thermodynamic explanation of the universal correlation between oxygen evolution activity and corrosion of oxide catalysts

Abstract

In recent years, the oxygen evolution reaction (OER) has attracted increased research interest due to its crucial role in electrochemical energy conversion devices for renewable energy applications. The vast majority of OER catalyst materials investigated are metal oxides of various compositions. The experimental results obtained on such materials strongly suggest the existence of a fundamental and universal correlation between the oxygen evolution activity and the corrosion of metal oxides. This corrosion manifests itself in structural changes and/or dissolution of the material. We prove from basic thermodynamic considerations that any metal oxide must become unstable under oxygen evolution conditions irrespective of the pH value. The reason is the thermodynamic instability of the oxygen anion in the metal oxide lattice. Our findings explain many of the experimentally observed corrosion phenomena on different metal oxide OER catalysts.

Figure 1. Schematic representation of the proposed LOER cation cycle.

This cycle could lead to the formation of a 3-dimensional interface layer between the bulk metal oxide lattice and the electrolyte. The remaining metal cations from LOER can participate in the LOER cation cycle by recombination with aqueous oxygen anions or they can dissolve in the electrolyte either with unchanged valency or, after an additional oxidation step, in a higher valence state.