Engineering strong metal-support interaction (SMSI) is a powerful strategy for enhancing the activity and durability of platinum catalysts under industrial alkaline hydrogen evolution conditions, yet controllable fabrication of such interfaces remains challenging. Here, we report a liquid gallium-mediated vapor deposition approach that induces pronounced SMSI between ultrafine platinum nanoparticles and nickel oxide supported on nickel foam. The liquid Ga layer acts as a dynamic transport medium that regulates precursor diffusion and decomposition, enabling controlled nucleation of 1.77 nm Pt nanoparticles and promoting interfacial electronic coupling with the NiO support. Spectroscopic analysis and theoretical calculations reveal charge redistribution across the Pt-NiO interface, leading to modified hydrogen adsorption energetics and a reduced water dissociation energy barrier. The resulting catalyst achieves an overpotential of 20 mV at 10 mA cm^-2 and sustains stable operation for 800 h at 500 mA cm^-2 in alkaline electrolyte. When implemented in an anion-exchange membrane water electrolyzer, the catalyst maintains ampere-level current densities with excellent durability. This work demonstrates liquid metal-mediated vapor deposition as a versatile platform for inducing strong metal-support interaction in ultrafine electrocatalysts for high-current alkaline energy conversion.

The coexistence of multi-component active sites like single-atom sites, diatomic sites (DAS) and nanoclusters is shown to result in superior performances in the hydrogen evolution reaction (HER). Metal diatomic sites are more complex than single-atom sites but their unique electronic structures can lead to significant enhancement of the HER kinetics. Although the synthesis and identification of DAS is usually challenging, we report a simple access to a diatomic catalyst by anchoring Co-Ru DAS on nitrogen-doped carbon supports along with Ru nanoparticles (NPs). Experimental and theoretical results revealed the atomic-level characteristics of Co-Ru sites, their strong electronic coupling and their synergy with Ru NPs within the catalyst. The unique electronic structure of the catalyst resulted in an excellent HER activity and stability in alkaline media. This work provides a valuable insight into a widely applicable design of diatomic catalysts with multi-component active sites for highly efficient HER electrocatalysis.