Ultrathin Iridium Nanosheets on Titanium Oxide for High-Efficiency and Durable Proton Exchange Membrane Water Electrolysis.

Reducing iridium (Ir) usage is essential for the commercial viability of proton exchange membrane water electrolysis (PEMWE), where the oxygen evolution reaction (OER) is a major performance and cost bottleneck. Conventional Ir nanoparticles (∼5 nm) suffer from low dispersion and limited surface utilization. Here, we report a catalyst architecture comprising ultrathin Ir nanosheets (Ir NS) supported on spherical TiO2 particles (Ir NS/TiO2). The ∼100 nm TiO2 particles effectively disperses 1-3 μm-wide, sub 2 nm-thick Ir nanosheets, ensuring full surface exposure and continuous electron transport, despite the intrinsically low conductivity of TiO2. The Ir NS/TiO2 catalyst exhibits enhanced OER activity and durability in both half-cell and PEMWE single-cell configurations. At an Ir loading of 0.7 mgIr cm-2, Ir NS/TiO2 achieves 3.6 A cm-2 at 1.8 V, significantly outperforming commercial Ir nanoparticles (Ir NP, 2.6 A cm-2). Long-term operation at 1.0 A cm-2 over 1000 h shows a low voltage decay rate of 0.095 mV h-1, compared to 0.414 mV h-1 for Ir NP. Moreover, Ir NS/TiO2 with an Ir loading amount of 0.5 mgIr cm-2 delivers comparable performance to Ir NP at 1.4 mgIr cm-2. These results present Ir NS/TiO2 as a highly efficient and durable OER catalyst, supporting its potential for cost-effective, scalable green hydrogen production.