Molecular O Dimers and Lattice Instability in a Perovskite Electrocatalyst.

Structural degradation of oxide electrodes during the electrocatalytic oxygen evolution reaction (OER) is a major challenge in water electrolysis. Although the OER is known to induce changes in the surface layer, little is known about its effect on the bulk of the electrocatalyst and its overall phase stability. Here, we show that under OER conditions, a highly active SrCoO electrocatalyst develops bulk lattice instability, which results in the formation of molecular O dimers inside the bulk and nanoscale amorphization induced via chemo-mechanical coupling.