Rational design of Ru species on N-doped graphene promoting water dissociation for boosting hydrogen evolution reaction

In this study, the morphological distribution of Ru on nitrogen-doped graphene (NG) could be rationally regulated via modulating the combination mode between Ru precursor and the zeolite imidazolate framework-8 (ZIF-8). The cation exchange and host-guest strategies respectively resulted in two different combination modes between Ru precursor and ZIF-8 anchored on graphene. Following pyrolysis of the above precursors, Ru single-atom sites (SASs) with and without Ru nanoparticles (NPs) were formed selectively on NG (denoted as Ru SASs+NPs/NG and Ru SASs/NG, respectively). Ru SASs+NPs/NG exhibited excellent hydrogen evolution reaction (HER) performance in alkaline solutions (η10=12 mV, 12.57 A mg−1Ru at 100 mV), which is much better than Ru SASs/NG. The experimental and theoretical study revealed that Ru SASs could adsorb hydrogen with optimal adsorption strength, while Ru NPs could lower the barrier of water molecule dissociation, and thus Ru SASs and Ru NPs could synergistically promote the catalytic performance of HER in alkaline solutions.