Cation-Exchange Method Enables Uniform Iridium Oxide Nanospheres for Oxygen Evolution Reaction

Polymer electrolyte membrane (PEM) water electrolyzers are a key technology for driving the energy system toward a renewable resource-based model. Numerous past and ongoing R&D activities have sought to reduce their dependence on precious metal catalysts, but unfortunately, there has still been no breakthrough in electrocatalyst design for PEM water electrolyzers. Scarce iridium remains the best choice as an electrocatalyst, thanks to its efficiency and durability for hosting the oxygen evolution reaction (OER). In this study, we present a synthesis method for preparing an iridium nanostructure that utilizes it more efficiently. A highly uniform morphology of IrO2 nanospheres was achieved based on a cation-exchange reaction and using a sacrificial template. This highly simple synthesis enabled a high concentration of hydroxide groups on the surface without additional treatment to be achieved, which plays a significant role in enhancing OER, as electrocatalysts present a 3-fold increase in mass activity compared to commercial IrO2. This study provides insights into the synthesis of nanostructures, with much potential to apply these to different applications. Moreover, we draw attention to the fundamental importance of structural properties with this simple but uniform structure and its performance as an electrocatalyst.