Electronic structures engineering of single atomic Ru by Ru nanoparticles to enable enhanced activity for alkaline water reduction

Regulation of the electronic structures of metal centers represents a robust strategy for enhancing the activity of electrocatalysts. Herein, we report the crafting of hybrid electrocatalysts comprising both single atomic Ru (SA-Ru) and Ru nanoparticles (NPs) supported on porous N-doped carbon (PC), in which the electronic structures of SA-Ru were effectively optimized by nearby Ru NPs to achieve great enhancement of the hydrogen evolution reaction (HER). The resulting SA-Ru/Ru NPs/PC displayed ultrahigh activity for HER in 1 M KOH with a mass activity of 4.2 mA mu g(Ru)(-1) at -0.07 V vs. RHE; this activity was 14 times that of commercial Pt/C, representing the largest reported value among the Pt-free electrocatalysts. In addition to the ultrahigh activity, the composite possessed the outstanding stability of 24 h and rapid HER kinetics (i.e. Tafel slope: 31.8 mV dec(-1)). The experimental and theoretical results matched well with each other and unambiguously indicated that the control over the electronic structures of SA-Ru and the advantageous PC support (i.e. its hierarchical porous nanostructures and superhydrophilic surface) jointly contributed to the exceptional performance.