Nitrogen-anchored dense Ru clusters synergized with atomic Zn sites for size stabilization and enhanced hydrogen evolution kinetics

Metal nanoclusters supported on solid matrices are highly promising for catalysis due to their exceptional atomic utilization efficiency and synergistic multi-site functionality. However, their practical deployment is often hindered by the limited capability of conventional supports to precisely regulate cluster loading sites, size, and density, which stems from randomly distributed defects and weak precursor-support interactions. In this work, we introduce a “single-atom rivet” strategy on a porous Zn-N-C support that enables the controlled synthesis and stabilization of ultrahigh-density Ru nanoclusters with tunable sizes. This is achieved by leveraging the strong metal–support interaction from N atoms and the atomic-scale confinement from isolated Zn sites. These atomic rivets provide steric confinement that effectively suppresses cluster migration and facilitate electron transfer from Ru to Zn, thereby modulating the electronic structure. Size-dependent mechanistic studies further reveal an inverse volcano relationship between the Ru cluster size and the d -band center position, with nanoclusters optimally balancing H 2 O dissociation and H*/OH* intermediate adsorption/desorption kinetics in the alkaline hydrogen evolution reaction. The resulting Ru/Zn-N-C–1.42 catalyst achieves an ultralow overpotential of 13.6 mV at 10 mA cm −2 and delivers an industrial-grade current density of 1.0 A cm −2 at only 1.65 V in an anion-exchange membrane water electrolyzer, exhibiting approximately twice the mass activity of commercial 20 wt% Pt/C. This work establishes a general “single-atom rivet” approach for stabilizing dense nanoclusters, offering a versatile platform for the design of high-performance catalysts in energy conversion and beyond. • A Novel Atomic-Level Design Paradigm: Introducing a precise strategy that moves beyond conventional defect engineering to simultaneously control the size and electronic structure of sub-nano clusters. • Deciphering a Size-Activity Volcano Relationship: Uncovering an inverse volcano trend via in-situ spectroscopy and theory, identifying the optimal Ru13 cluster for balancing catalytic steps. • Exceptional Performance from Lab to Device: Achieving record-low overpotential (13.6 mV) superior to Pt/C, high efficiency at industrial current densities, and validated stability in a practical electrolyzer.