Carbon dot-driven spatial and electronic modulation of Ru on graphene for pH-universal hydrogen evolution reaction electrocatalysts

Abstract

The development of efficient pH-universal electrocatalysts for the hydrogen evolution reaction (HER) remains a critical challenge in renewable energy technologies. While Pt-based catalysts exhibit exceptional activity in acidic media, their performance deteriorates significantly under alkaline and neutral conditions due to sluggish water dissociation kinetics. Herein, a carbon dot (CD)-driven strategy was developed to engineer the spatial distribution and electronic structure of Ru species on graphene, achieving remarkable HER activities across the full pH range. By modulating the Ru–CD interfacial configuration from CDs@Ru-coated to Ru&CD-dispersed and Ru@CD-encapsulated structures, it was found that Ru-6CDs/G exhibits excellent performance with the planar Ru&CDs arrangement. This Ru-6CDs/G catalyst exhibits ultralow overpotentials of 77 mV (0.5 M H₂SO₄), 58 mV (1.0 M KOH), and 39 mV (0.5 M PBS) at 10 mA cm⁻², alongside exceptional mass activities surpassing those of commercial Pt/C by up to 129 times. Combined experimental and theoretical analyses reveal that the Ru&CDs configuration with optimal dispersion and the smallest size (∼1.14 nm) of Ru nanoparticles induces a moderate d-band center position, balancing hydrogen adsorption/desorption energetics and accelerating the Volmer–Heyrovsky pathway. Density functional theory (DFT) calculations further demonstrate that charge redistribution at the Ru–CD interface enhances H* intermediate stabilization, while COHP analysis confirms optimization of the Ru–H bond strength. This work not only establishes a universal design principle for metal–CD hybrid catalysts but also provides deep insights into the electronic and spatial regulation of active sites for advanced electrocatalysis.