Operando X-ray absorption spectroscopy: A powerful tool toward water splitting catalyst development

The development of electrocatalysts for the electrochemical splitting of water is of high importance in order to meet the energy storage demands imposed by the growth of intermittent renewable energy sources. In situ/operando X-ray absorption spectroscopy (XAS) is a powerful technique with the potential of revealing the electronic and geometric structure of nanoparticulate electrocatalyst systems under gas-evolving conditions, thereby providing vital insight into the nature of the catalytic active site in the oxygen evolution reaction (OER) on oxide-based electrocatalysts. This article provides an overview detailing the recent applications of operando XAS as applied to the OER for state-of-the-art acid membrane and alkaline electrolyte systems. In doing so, we portray the fundamental studies that have assisted in the identification of key reactive species participating in the OER for IrO2-based acidic electrolyte systems and those that have aided in elucidating the role of Fe in Fe-Ni oxide alkaline electrolyte systems.