Utilizing platinum group metal single-atom catalysts to advance electrochemical oxygen evolution reaction

Using renewable electricity to produce green hydrogen through water electrolysis has emerged as a potential approach towards transitioning to sustainable fuel sources. Overall water electrolysis consists of an oxygen evolution reaction (OER) and a hydrogen evolution reaction (HER), with research efforts predominantly focusing on the former due to its sluggish kinetics and high overpotentials, which hinders the scalability efforts of water electrolysis applications. The use of platinum group metals (PGM), notably iridium (Ir), in electrocatalytic water oxidation has demonstrated excellent performance. However, the scarcity and associated high cost hampers widespread adoption of PGM-based electrocatalysts. Recently, attention has shifted towards the use of PGM single-atom catalysts (SACs), whereby the maximized PGM atom utilization enhances the activity towards OER, while reducing the cost element significantly. In this work, we present an efficient Ir-based SAC synthesized via wet chemistry atop a support composed of a combination of transition metals. Performance evaluations conducted in an alkaline electrolyte (1M KOH) revealed high activity towards OER, outperforming benchmark OER catalysts. Notably, the prepared Ir@NiCoMo@NF electrocatalyst, in both oxide and nitride forms, exhibited low OER overpotentials of 260 and 270 mV vs. RHE, respectively, to achieve a current density of 10 mA cm^-2, as well as low Tafel slopes of 49.3 and 67.8 mV dec^-1, respectively. To explain the high activity and gain insights into the intrinsic properties of the electrocatalyst, an array of advanced characterization techniques was employed, including TEM, SEM, XPS, and XRD. The findings presented herein highlight the potential of PGM-based SACs in advancing OER towards efficient and cost-effective production of green hydrogen from water electrolysis.