Engineering Ru@Ir Core–Shell Nanoparticles on Titanium Oxynitride–Graphene Support for a Highly Active and Durable pH-Universal Hydrogen Evolution Reaction

The rational design of electrocatalysts with high activity, durability, and low precious metal content is key to advancing hydrogen production via water electrolysis. Here, we present a multifunctional electrocatalyst based on Ru@Ir core-shell nanoparticles anchored on a conductive titanium oxynitride-graphene hybrid support (Ru@Ir/TiO _x N _y -C), achieving superior performance for the hydrogen evolution reaction (HER) in both acidic and alkaline media. The combination of the core-shell Ru@Ir architecture and the strong metal-support interaction (MSI) with TiO _x N _y optimizes hydrogen and hydroxide adsorption energies, as confirmed by X-ray photoelectron spectroscopy and density functional theory (DFT) calculations. In alkaline media, Ru@Ir/TiO _x N _y -C outperforms commercial Pt/C with a remarkably low overpotential of 13 mV at 10 mA cm^-2 and high mass activity, while in acidic conditions, it rivals Pt/C and surpasses monometallic analogs. The long-term stability of the composite is attributed to the enhanced nanoparticle anchoring and structural integrity provided by the TiO _x N _y support. This work shows that combining core-shell nanostructures with engineered conductive supports can effectively replace platinum in HER applications. Such a nanocomposite strategy offers a versatile platform for the development of advanced electrocatalysts across a broad range of energy conversion reactions.