Advanced iridium catalysts on multi-porous tantalum oxide supports for efficient proton exchange membrane water electrolysis

Reducing the loading of precious metals such as Ir and Pt while maintaining the performance of membrane electrode assembly (MEA) with highly active oxygen evolution reaction (OER) catalysts is a significant challenge in the development of efficient proton exchange membrane water electrolyzers (PEMWEs). This study presents a highly active and cost-effective catalyst consisting of iridium supported on multi-porous tantalum oxide (M−Ta₂O₅), which integrates both macropores and mesopores. The iridium nanostructures supported on the M−Ta₂O₅ enhance the utilization of Ir and exhibit larger electrochemical surface areas. With a 30 wt% Ir loading, the Ir/M−Ta₂O₅ catalyst demonstrates an overpotential of 290.4 ± 3.5 mV at a current density of 10 mA cm⁻² and a mass activity of 730.5 ± 44.6 A g_Ir⁻¹ at 1.55 V_RHE. Consequently, Ir/M−Ta₂O₅ can be effectively utilized to fabricate MEA with an Ir loading of 0.2 mg cm⁻² and Nafion® 115 membrane. At the single-cell level, this catalyst achieves a current density of 2.5 A cm⁻² at 1.89 V, underscoring the potential of Ir/M−Ta₂O₅ as a highly efficient and cost-affordable OER catalyst. This work highlights the promise of Ir/M−Ta₂O₅ in reducing the reliance on precious metals, thereby contributing to the economic and environmental sustainability of PEMWEs.