Boron‐Induced Interstitial Effects Drive Water Oxidation on Ordered Ir‐B Compounds

Abstract Interstitial filling of light atoms strongly affects the electronic structure and adsorption properties of the parent catalyst due to ligand and ensemble effects. Different from the conventional doping and surface modification, constructing ordered intermetallic structures is more promising to overcome the dissolution and reconstruction of active sites through strong interactions generated by atomic periodic arrangement, achieving joint improvement in catalytic activity and stability. However, for tightly arranged metal lattices, such as iridium (Ir), obtaining ordered filling atoms and further unveiling their interstitial effects are still limited by highly activated processes. Herein, we report a high‐temperature molten salt assisted strategy to form the intermetallic Ir−B compounds (IrB 1.1 ) with ordered filling by light boron (B) atoms. The B residing in the interstitial lattice of Ir constitutes favorable adsorption surfaces through a donor‐acceptor architecture, which has an optimal free energy uphill in rate‐determining step (RDS) of oxygen evolution reaction (OER), resulting in enhanced activity. Meanwhile, the strong coupling of Ir−B structural units suppresses the demetallation and reconstruction behavior of Ir, ensuring catalytic stability. Such B‐induced interstitial effects endow IrB 1.1 with higher OER performance than commercial IrO 2 , which is further validated in proton exchange membrane water electrolyzers (PEMWEs).