Dopant-Assisted Control of the Crystallite Domain Size in Hollow Ternary Iridium Alloy Octahedral Nanocages toward the Oxygen Evolution Reaction

Abstract

Kwon et al. demonstrate that the structural evolution of Ir-oxide nanocatalysts during OER depends on the crystallinity of the precursor Ir-alloy nanostructures. The loosely knit IrO2@amorphous-IrOx structure, derived from the polycrystalline ternary Ir-alloy nanocage, exhibits high OER activity as well as long-term stability. ？ 2020 The Author(s)The dissolution of Ir-oxide-based catalysts remains a roadblock in the development of durable electrocatalytic oxygen evolution reaction (OER) catalysts. Both the activity and stability of Ir-based catalysts are critically dependent on the ratio of stable rutile IrO2 and unstable amorphous Ir oxide (a-IrOx), as well as the spatial relationship between them. Here, we report that the domain size in hollow ternary Ir alloy nanocages can be fine-tuned by the introduction of dopant elements during the growth of parent core-shell nanoparticles, Cu@CuIr. After electrochemical oxidation under OER conditions, Ir alloy nanocages possessing multiple crystallites in their structure are transformed into hollow aggregates of loosely knit crystalline IrO2@a-IrOx domains, whereas single-crystalline Ir alloy nanocages are transformed to hollow Ir oxides with a random mixture of a-IrOx and IrO2. The loosely knit IrO2@a-IrOx structure achieves high OER activity and long-term stability, which is not feasible with the random mixture of a-IrOx and IrO2. ？ 2020 The Author(s)