Reversible and irreversible transformations of Ni-based electrocatalysts during the oxygen evolution reaction

Nickel-based catalysts for the alkaline oxygen evolution reac-tion (OER) demonstrate excellent catalytic performance and stability. However, a lack of fundamental understanding of the dynamic electronic and structural changes that occur under OER conditions inhibits the rational design of new materials. Recent advances in operando spectroscopy and computa-tional modeling techniques have helped to elucidate the electrochemically-driven transformations of Ni-based mate-rials. For reversible transformations, this encompasses an increased understanding of the redox transformations of Ni/Fe centers, the adsorption and desorption of reaction in-termediates, oxygen vacancy dynamics, phase trans-formations, and the mechanism of dissolution and redeposition of surface atoms. Likewise, there have been great advances in scientific understanding of irreversible transformations including phase transformations related to ageing, as well as operando surface reconstruction which involves the growth of new OER active phases.