Crystal-phase engineering of nanowires and platelets of KxIrO2 for efficient water oxidation

Nanostructuring electrocatalysts based on precious metals can be an effective tool to increase the dispersion and hence increase the mass activity. Here, we demonstrate the crystal phase engineering of two different potassium iridates polymorphs. We develop a selective solid-state synthesis of either a 1-dimensional K0.25IrO2 nanowires with a hollandite crystal structure, or 2-dimensional KIrO2 hexagonal platelets. Both structures present increased specific and mass electrocatalytic activity for water oxidation reaction in acidic media compared to commercial rutile IrO2 of up to 40%, with the 1D nanowires outperforming the 2D platelets. XANES, EXAFS and XRD investigations prove the structural stability of these two different allotropes of K-IrO2 compounds upon electrocatalytic testing. These low dimensional nanostructured 1D and 2D KxIrO2 compounds with superior mass activity to commercial IrO2 can pave the way towards the design of new electrocatalysts architectures with reduced Ir loading content for Proton Exchange Membrane water electrolyser anodes