(Invited) Interplay Between Strain, Electronic Structure, and Oxygen Evolution Electrocatalysis in Iridates

The sluggish kinetics of the oxygen evolution reaction (OER) is one of the major sources of the overpotentials in many air-breathing electrochemical energy devices such as electrolyzers and rechargeable metal-air batteries. To increase the OER kinetics and reduce the overpotentials, it is critical to establish the linkage between the catalyst structure and the OER activity and mechanism. In this contribution, we present our effort in establishing this structure-activity connection, using iridates as model electrocatalysts and strain as a tuning knob for understanding the structure-activity connection. We have grown a series of perovskite iridium oxides with different biaxial strains using Molecular Beam Epitaxy (MBE), which we will use as a model system to elucidate how the OER kinetics can be affected by strain. To further connect strain to the physical properties of the iridates, we subject these MBE-grown oxides to ambient pressure X-ray photoelectron spectroscopy, from which we can determine how strain can affect the oxygen adsorption. We use this information to reveal insights into how strain can serve as a material knob to facilitate the OER and the underlying structure-activity relationship in iridates.