Constructing Highly Porous Low Iridium Anode Catalysts Via Dealloying for Proton Exchange Membrane Water Electrolyzers

Iridium (Ir) is the most active and durable anode catalyst for the oxygen evolution reaction (OER) for proton exchange membrane water electrolyzers (PEMWEs). However, their large-scale applications are hindered by high costs and scarcity of Ir. Lowering Ir loadings below 1.0 mgcm^-2 causes significantly reduced PEMWE performance and durability. Therefore, developing efficient low Ir-based catalysts is critical to widely commercializing PEMWEs. Herein, an approach is presented for designing porous Ir metal aerogel (MA) catalysts via chemically dealloying IrCu alloys. The unique hierarchical pore structures and multiple channels of the Ir MA catalyst significantly increase electrochemical surface area (ECSA) and enhance OER activity compared to conventional Ir black catalysts, providing an effective solution to design low-Ir catalysts with improved Ir utilization and enhanced stability. An optimized membrane electrode assembly (MEA) with an Ir loading of 0.5 mg_Ir cm^-2 generated 2.0 A cm^-2 at 1.79 V, higher than the Ir black at a loading of 2.0 mg_Ir cm^-2 (1.63 A cm^-2). The low-Ir MEA demonstrated an acceptable decay rate of ≈40 µV h^-1 during durability tests at 0.5 (>1200 h) and 2.0 A cm^-2 (400 h), outperforming the commercial Ir-based MEA (175 µV h^-1 at 2.0 mg_Ir cm^-2).