A Route to Complex Materials Consisting of Multiple Crystalline Phases Ir‐Ru‐Ir_xRu_1‐xO₂ as Multifunctional Electrocatalysts

Abstract The synthesis of catalytic materials containing active sites of various oxidation states (metal, oxide, etc.) for the dual use in reduction and oxidation reactions remains challenging because most of the reported methods for the metallic state are often incompatible with those for the oxide state. A new methodology is reported for the synthesis of a library of bimetallic metal‐oxide materials containing three crystalline phases Ir‐Ru‐Ir_xRu_1‐xO₂ by combining the calcination under air and the polymerization of aniline in the presence of IrCl₃ and RuCl₃ precursors. Morphology, structure, and surface oxidation state studies (XRD, SEM/EDX, S/TEM, XPS) confirm the hypothesis that IrCl₃ evolves to Ir while RuCl₃ evolves to RuO₂ during the calcination under air. An Ir:Ru atomic ratio of 50:50 can be converted into a heterogeneous nanostructure composed of Ir, Ru, and Ir_xRu_1‐xO₂ to date, with remarkable catalytic activity for both hydrogen evolution reaction (HER) with a small overpotential of 40 mV and oxygen evolution reaction (OER) with a small overpotential of 290 mV at the metric current density of 10 mA cm⁻² in 0.5 m H₂SO₄. The results can serve as a platform for the development of efficient multifunctional materials for practical use in both catalytic oxidation and reduction reactions.