Optimizing the size and electronic effects of core-shell heterostructures via well-constructed Ru clusters encapsulated in N-doped carbon layers

The design and development of high-performance electrocatalysts for the hydrogen evolution reaction (HER) are essential for advancing the hydrogen economy. The electronic structure and core size of an electrocatalyst are pivotal for determining the intrinsic activity of the catalytic sites. Interfacial engineering, particularly the formation of well-controlled core-shell heterostructures, has emerged as a promising strategy, although significant challenges remain. Here, we present a series of Ru@NC heterostructures with size-controlled Ru cores encapsulated in N-doped graphene layers. Among these, Ru@NC-3h, with the best holistic effects, has superior durability and mass activity 7.03 times that of Pt/C. This high performance is attributed to the open porous structure, which enhances active site exposure and mass transfer, and the optimized adsorption and desorption of reaction intermediates by the strengthened hetero-interfacial interaction between the smaller Ru cores and thin N-doped shells. Attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveals reinforced interfacial water interaction and reduced hydrogen adsorption. Density functional theory (DFT) calculations indicate that the size effect promotes interfacial H2O adsorption, whereas the electronic effect governs *H adsorption to collectively accelerate the HER kinetics. This novel strategy, introduced to regulate heterostructures through size and electronic effects, offers significant potential for various energy material applications. We present new size-controlled Ru@NC heterostructures with optimized size and electronic effects for superior HER performance. DFT calculations indicate that the size effects promote interfacial H2O adsorption, whereas the electronic effects mainly optimize *H adsorption. These predictions are in agreement with the potential-dependent ATR-SEIRAS analysis, which indicates that holistic effects are collectively responsible for enhancing HER kinetics. [Display omitted]