Interfacial synergy between Ru³ ⁺-doped NiOOH lattice and surface Ru nanoparticles: Unveiling hydrogen spillover pathways for high current density alkaline hydrogen evolution reaction

The development of hydrogen evolution reaction (HER) catalysts operating under high current densities is critical for advancing industrial water electrolysis toward green hydrogen production. Herein, we report an ultra-stable hierarchical electrocatalyst Ru/(Ni 1- x Ru x )OOH on anodized nickel mesh (ANM) via a facile two-step anodization-substitution strategy. The catalyst features dual Ru active sites: lattice-doped Ru 3 + within the NiOOH framework and surface-deposited metallic Ru nanoparticles (NPs), supported by a hierarchical porous architecture derived from anodization. The optimized Ru/(Ni 1- x Ru x )OOH catalyst exhibits exceptional alkaline HER activity, with a low overpotential of 81 mV at 100 mA cm −2 . More importantly, it shows remarkable stability at a large current density of 1 A cm −2 for 500 h with a current decay rate of 0.1 mV h −1 , outperforming most of the state-of-the-art HER electrocatalysts. In situ Raman spectroscopy and density functional theory (DFT) calculations show that Ru 3+ doping modulates the electronic environment of NiOOH lattice O atoms, which accelerate H 2 O dissociation and generate H* intermediates adsorbed on O sites (*H-O). Thereafter, H* spills over to adjacent Ru NPs via Ni-O-Ru bonds, forming adsorbed *H-Ru 0 intermediates. These *H-Ru 0 species then accept electrons from Ni, which drives their recombination into H 2 . Additionally, weakly hydrogen-bonded interfacial water (2-HB-H 2 O and free-H 2 O) ensures a continuous supply of reactant to the active sites. This work provides a strategy for designing Ni-based electrocatalysts with tailored active sites and hierarchical structures, advancing alkaline water electrolysis at industrial-level current densities.