High-Performance Hydrogen Evolution by Ru Single Atoms and Nitrided-Ru Nanoparticles Implanted on N-Doped Graphitic Sheet

The most efficient electrocatalyst for the hydrogen evolution reaction (HER) is a Pt-based catalyst, but its high cost and nonperfect efficiency hinder wide-ranging industrial/technological applications. Here, an electrocatalyst of both ruthenium (Ru) single atoms (SAs) and N-doped-graphitic(G_N)-shell-covered nitrided-Ru nanoparticles (NPs) (having a Ru-N_x shell) embedded on melamine-derived G_N matrix {1: [Ru(SA)+Ru(NP)@RuN_x@G_N]/G_N}, which exhibits superior HER activity in both acidic and basic media, is presented. In 0.5 m H₂SO₄/1 m KOH solutions, 1 shows diminutive “negative overpotentials” (−η = |η| = 10/7 mV at 10 mA cm⁻², lowest ever) and high exchange current densities (4.70/1.96 mA cm⁻²). The remarkable HER performance is attributed to the near-zero free energies for hydrogen adsorption/desorption on Ru(SAs) and the increased conductivity of melamine-derived G_N sheets by the presence of nitrided-Ru(NPs). The nitridation process forming nitrided-Ru(NPs), which are imperfectly covered by a G_N shell, allows superb long-term operation durability. The catalyst splits water into molecular oxygen and hydrogen at 1.50/1.40 V (in 0.1 m HClO₄/1 m KOH), demonstrating its potential as a ready-to-use, highly effective energy device for industrial applications.