Designing of Hexagonal Nanosheets with Edge‐Sharing [IrO6] Octahedral Crystals for Efficient and Stable Acidic Water Splitting

Abstract The oxygen evolution reaction (OER) is a critical factor for advancing the industrial application of proton exchange membrane (PEM) electrolyzers. However, the low mass activity of iridium‐based catalysts has become a critical obstacle in improving the efficiency of the OER. To address this problem, a hexagonal system nanosheet structure with lattice distortion and edge‐connected [IrO 6 ] octahedron is designed to enhance both mass activity and durability. This material exhibits a high mass activity of 217 mA mg Ir −1 at 1.55 V relative to the reversible hydrogen electrode (RHE), which is 13 times greater than that of Rutile IrO 2 . Furthermore, the voltage of T‐CsIr exhibits no significant increase after 400 h of continuous operation at a current density of 10 mA cm −2 . Integrating X‐ray experimental analysis with theoretical calculations reveals that the shortening of the Ir─Ir bond and the reduction of Ir 3+ proportion effectively modulate the adsorption energy of the rate‐determining step, thereby significantly promoting the kinetics of the OOH * deprotonation process. These results demonstrate that regulation of lattice distortion is a feasible approach to effectively improve the OER catalytic performance.