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 (RuN 4 ) 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 (ΔG H*  = –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.