Ultrafine Ru nanoclusters supported on N/S doped macroporous carbon spheres for efficient hydrogen evolution reaction.

The construction of highly-active and stable electrocatalysts for the hydrogen evolution reaction (HER) is significant for efficient water splitting processes. Herein, we develop an efficient HER catalyst of ultrafine Ru nanoclusters supported on a N/S doped macroporous hollow carbon sphere (Ru/H-S,N-C). The N/S co-doping strategy not only facilitates the reduction of the Ru nanocluster sizes, but also regulates the electronic structure of metallic Ru, improving the HER activity of the metallic Ru catalyst. Due to the structural advantages of N/S-doped macroporous carbon spheres that provide a fast mass transfer process and the high intrinsic activity of Ru nanoclusters, the optimized Ru/H-S,N-C catalyst exhibits excellent HER performance in alkaline medium, with a low overpotential of 32 mV to reach 10 mA cm, fast HER kinetics (a Tafel slope of 24 mV dec) and excellent durability, superior to the performances of the Ru/H-N-C sample and commercial Pt/C catalyst. Our work offers some guidance on the design of efficient Ru-based electrocatalysts.