High-Porosity, Layered Iridium Oxide as an Efficient, Durable Anode Catalyst for Water Splitting

Lowering iridium (Ir) loading without sacrificing activity and durability is critical to the future development of proton exchange membrane water electrolyzer (PEMWE). Here, we present the synthesis of iridate-derived, layered iridium oxide microparticles (dubbed p-L-IrO₂) with a high open porosity of approximately 74% and their structural advantages for the fabrication of efficient, durable, low-Ir-loading anode catalytic layer in PEMWE. The p-L-IrO₂ material is synthesized by an easily scalable route involving acid treatment of alkali metal salt-templated iridates that form in mixed alkali metal nitrates-hydroxides at low temperature. The combination of high-porosity morphology and layered structure in the material preferentially exposes a high density of hydroxylated edge sites, which are catalytically active and stable to achieve the oxygen evolution reaction via a structurally hydroxyl group-participated adsorbate evolution mechanism. This material is further demonstrated to enable the fabrication of low-Ir-loading anode catalytic layers in PEMWE, which can afford excellent catalytic performance (2.7 A cm^-2@1.9 V@80 °C; membrane: Nafion™ N115) due to the simultaneous reduction of activation and mass transport losses and retention of catalytic activity for 2300 h at 1.0 A cm^-2 current density. © 2024 Chinese Chemical Society.