Engineering Ru@Ir core–shell nanoparticles on titanium oxynitride–graphene support for a highly active and durable pH-universal hydrogen evolution reactionPopović, Aleksandra S. (Avtor) Marić, Ivan (Avtor) Bele, Marjan (Avtor) Rems, Ervin (Avtor) Huš, Matej (Avtor) Pavko, Luka (Avtor) Ruiz-Zepeda, Francisco (Avtor) Bijelić, Lazar (Avtor) Grgur, Branimir (Avtor) Hodnik, Nejc (Avtor) Smiljanić, Milutin (Avtor) hydrogen evolution reactioniridiumrutheniumcore−shell structuresTiO$_x$N$_y$MSIDFTcatalystsevolution reactionsnanoparticlesoxidestransition metalsThe 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.20252025-12-03 14:40:55Članek v reviji176557sl