Ru-Loaded Highly Graphitized Porous Carbon with High Pyrrolic-N Content for Superb Electrochemical Hydrogen Evolution

Abstract

The performance of electrocatalysts is closely related to their supporting materials since their properties such as heteroatom doping, porosity, graphiticity, and electrical conductivity play a decisive role on catalyst performance. We report here the preparation of N-doped highly graphitized porous network-structured carbon (N-HGC) as a catalyst support for Ru nanoparticles (NPs) catalytically active for hydrogen evolution reaction (HER) using simple pyrolysis of g-C3N4 in the presence of Mg metal. The as-prepared N-HGC shows high graphiticity confirmed by XRD and Raman analyses, high electrical conductivity, and large surface area along with large amount of open mesopores, containing the proper amount of N doping rich with high pyrrolic-N content for homogeneous distribution of Ru NPs. This Ru/N-HGC catalyst shows a remarkably low overpotential of 9.6 mV (vs RHE) at 10 mA/cm2, which is near ideal and far better than state-of-the-art Pt/C. It also illustrates superb stability, maintaining the HER activity for 200 h and 10k CV cycles without any significant degradation. This superb HER performance is attributed to the robust N-HGC support featuring thin carbon structure, high electrical conductivity, suitable porosity, and N pyrrolic doping. The atomistic basis for the low overpotential is explained via Grand Canonical Quantum Mechanics (GC-QM) calculations. These calculations show that the pyrrolic-N in the support strengthens the coupling to Ru NP and weakens the binding of H to Ru NP, improving the rate determining Tafel reaction.