# Crystal-Phase Engineering of Nanowires and Platelets of K x IrO2 for Efficient Water Oxidation

## TL;DR

Researchers engineered nanowires and platelets of KxIrO2 to improve water oxidation efficiency, reducing the need for expensive iridium.

## Contribution

A novel solid-state synthesis method creates 1D and 2D KxIrO2 structures with enhanced electrocatalytic activity for water oxidation.

## Key findings

- 1D K0.25IrO2 nanowires show up to 40% higher activity than commercial IrO2.
- Both 1D and 2D KxIrO2 structures are structurally stable during electrocatalytic testing.
- Low-dimensional KxIrO2 structures could reduce iridium loading in PEMWE anodes.

## Abstract

IrO2 is
one of the most widely investigated electrocatalysts
for oxygen evolution reaction in an acidic environment. Increasing
the mass activity is an effective way of decreasing the loading of
Ir, to ultimately reduce costs. Here, we demonstrate the crystal-phase
engineering of two different potassium iridate polymorphs obtained
by designing a selective solid-state synthesis of either one-dimensional
K0.25IrO2 nanowires with a hollandite crystal
structure or two-dimensional KIrO2 hexagonal platelets.
Both structures present increased specific and mass electrocatalytic
activities for the water oxidation reaction in acidic media compared
to commercial rutile IrO2 of up to 40%, with the 1D nanowires
outperforming the 2D platelets. XANES, extended X-ray absorption fine
structure, and X-ray diffraction investigations prove the structural
stability of these two different allotropes of KxIrO2 compounds
upon electrocatalytic testing. These low-dimensional nanostructured
1D and 2D KxIrO2 compounds with superior mass activity
to commercial IrO2 can pave the way toward the design of
new electrocatalyst architectures with reduced Ir loading content
for proton exchange membrane water electrolyzer (PEMWE) anodes.