Electronic reconfiguration of Ru single atoms by carbon-confined Ru nanoparticles enables pH-universal hydrogen evolution.

The hydrogen evolution reaction (HER) is critical for clean energy conversion, yet achieving efficient and durable electrocatalysis across a wide pH range remains a major challenge. Modulating the electronic structure of metal single atoms has shown promise, but is often constrained by weak metal-support interactions in conventional carbon matrices. Here, we report a pH-universal HER electrocatalyst comprising atomically dispersed Ru sites and carbon-confined Ru nanoparticles, synthesized via one-step pyrolysis of biomass-derived precursors. The catalyst delivered low overpotentials of 176 mV (Tafel slope: 23 mV dec-1) in acidic and 241 mV (40 mV dec-1) in alkaline media at 200 mA cm-2, along with outstanding operational stability exceeding 500 hours-outperforming commercial Pt/C. This performance arises from electron-rich Ru single atoms (RuN4) modulated by neighboring Ru nanoparticles, synergistically embedded within a hydrophilic and porous carbon scaffold. Density functional theory (DFT) calculations revealed a near-optimal hydrogen adsorption free energy (ΔGH* = -0.25 eV) in acidic conditions and a moderate water dissociation barrier (0.94 eV) in alkaline media. Our findings demonstrate a viable strategy for integrating nanoparticles and single atoms to achieve both high activity and durability, while highlighting the upcycling of biomass into advanced HER catalysts via rational interface engineering.