Advances in iridium single-atom catalysts for the electrochemical oxygen evolution reaction

Single-atom catalysts (SACs) have emerged as highly versatile catalytic materials for enhancing many industrially relevant electrochemical reactions. This review highlights recent advancements in the development of iridium SACs, primarily for water splitting applications. By reducing iridium to the single atom scale, the inherent beneficial scaling relationships can be preserved while substantially reducing precious metal loading to achieve mass activity as high as 2511 A g_Ir^-1. The single-atom character also allows for unique electronic and coordination interactions, resulting in oxidation states surpassing Ir(V) and enhancement of the lattice oxygen implementation, expanding the parameters for electrochemical performance optimization. Through this optimization, one highlighted catalyst was able to achieve an overpotential of 144 mV at 10 mA cm^-2 for the oxygen evolution reaction, resulting in hydrogen generation surpassing the Department of Energy targets. Although currently limited by synthetic obstacles, the recent advances in Ir SACs highlighted in this review aim to show potential pathways towards commercial applications, contributing to the widespread implementation of zero emission hydrogen fuels.