Perchlorate Fusion–Hydrothermal Synthesis of Nano-Crystalline IrO2: Leveraging Stability and Oxygen Evolution Activity

Abstract

Iridium oxides are the leading oxygen evolution reaction (OER) electrocatalysts for proton-exchange-membrane water electrolyzers (PEMWEs). However, improving iridium utilization is crucial due to its high cost and scarcity. Crystalline rutile-type iridium dioxide (IrO2) offers superior stability in acidic OER conditions compared to amorphous iridium oxide (IrOx), but the high synthesis temperatures required for crystalline phase formation reduce OER activity by decreasing active surface area. Herein, we present a novel perchlorate fusion–hydrothermal (PFHT) synthesis method to produce nano-crystalline rutile-type IrO2 nanoparticles with exceptional OER performance. This low-temperature approach involves calcination 300 °C in the presence of a strong oxidizing agent, sodium perchlorate, followed by hydrothermal treatment at 180 °C, yielding ~2 nm IrO2 nanoparticles. The catalyst achieved a high mass-specific OER activity of 95 A gIr–1 at 1.525 VRHE in ex situ glass-cell testing. Notably, the PFHT-synthesized IrO2 demonstrated remarkable stability under harsh accelerated stress test conditions, outperforming commercial catalysts. The exceptional activity of the catalyst was confirmed with in situ PEMWE single-cell evaluations. This demonstrates that the PFHT synthesis method leverages the superior intrinsic properties of nano-crystalline IrO2, effectively overcoming the typical trade-offs between OER activity and catalyst stability, making it a promising approach for advancing PEMWE technologies.