Dual-Atom-Doped Metastable Iridium Oxide with Multichamber Nanostructure for Durable Low-Iridium PEM Electrolyzers

The pursuit of efficient and durable proton exchange membrane water electrolysis (PEMWE) under ultralow Ir loadings is critically hindered by the intrinsic activity–stability trade-off of Ir-based oxygen evolution reaction (OER) catalysts and inefficient Ir utilization within low-loading anode catalyst layers. Herein, we report a class of Hf/Co dual-atom-doped multichamber 3R-IrO2 electrocatalysts by integrating mesoscale structural engineering with atomic-scale electronic regulation to achieve a durable low-Ir PEM electrolyzer. We demonstrate that the multichamber architecture lowers the effective volumetric Ir density and enlarges the electrochemically accessible interface, while dual-atom doping into the inherent defect-rich Ir–O framework enables robust OER activity. The experimental and theoretical results reveal that Hf preferentially stabilizes the Ir–O framework and suppresses excessive lattice-oxygen participation, whereas Co modulates the electronic structure of Ir to lower the rate-determining barrier of the adsorbate evolution mechanism, thereby synergistically enhancing catalytic activity and stability of metastable 3R-IrO2. A PEMWE device assembled with this catalyst delivers a cell voltage of 1.61 V at 1 A cm–2 with a low Ir loading of only 0.3 mgIr cm–2, and sustains stable operation for over 2000 h. This work establishes a multiscale electrocatalyst design paradigm for sustainable durable PEMWEs.