Rhenium-Doping to Promote Structural Evolution of Metallic Iridium to Oxides on Platinum Nanowire Bundles for Acidic Oxygen Evolution

The current high Ir loading (∼2 mg_Ir cm⁻²) in proton exchange membrane water electrolyzers (PEMWEs) severely hinders their applications for green hydrogen production. Reducing Ir loading while maintaining high performance and durability for the oxygen evolution reaction (OER) anode is critical for the Gigawatt-scale deployment of PEMWEs. Herein, we report an ultra-low Ir anode, consisting of Re-doped Ir nanoparticles anchored on Pt nanowire networks, enabling rational catalyst design at the atomic scale and electrode structure engineering at the nanoscale. The unique doping of Re into Ir was explored as an effective strategy to promote the desirable conversion from metallic Ir to amorphous IrO_x during the acidic OER, thus benefiting intrinsic activity and stability enhancements. Notably, the Pt nanowire bundles serve as a support to enhance electrical conductivity and provide a high-surface-area, robust, and interconnected electrode structure, significantly increasing Ir utilization and electron/mass transport at the device level. Three-electrode electrochemical tests revealed that the developed Ir catalyst exhibits a 100% increase in electrochemical surface area (ECSA) and a 160% enhancement in intrinsic OER activity compared to commercial Ir black catalysts. The optimized Ir anode achieved a current density of 3.0 A cm⁻² at 1.69 V (0.2 mg_Ir cm⁻²) and 1.73 V (0.1 mg_Ir cm⁻²) in membrane electrode assemblies (MEAs), exceeding the US DOE 2026 targets (0.5 mg_PGM cm⁻² at 1.8 V for 3.0 A cm⁻²). The corresponding MEAs also demonstrated compelling long-term durability, as evidenced by a low voltage degradation rate of 26 µV h⁻¹ over 1100 hours of operation and 0.8 µV cycle⁻¹ during an accelerated stress test.