- Selected as Journal Cover of July 2019

- Featured on Hot Topic: Water Splitting 

Abstract

 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 GN 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 HClO_​4/1 ​m KOH), demonstrating its potential as a ready‐to‐use, highly effective energy device for industrial applications.