Ru-loaded pyrrolic-N-doped extensively graphitized porous carbon for high performance electrochemical hydrogen evolution

Abstract

Herein, we report a novel methodology for preparation of new N-doped extensively graphitized porous carbon (N-GPC) as a new catalyst support for Ru nanoparticles (NPs) with dramatically improved hydrogen evolution reaction (HER) activity. Our method is remarkably simple: pyrolyzing g-C3N4 in the presence of Mg metal. Here, we show that Mg plays marvelous dual roles as a reducing agent to graphitize the g-C3N4 precursor at low temperature and as a precursor for Mg3N2, which generates network-structured porous carbon as a new porogen. This offers highly robust graphitized carbon with high electrical conductivity, network-structured high porosity, and proper N content, most desired as a catalyst support. As-prepared Ru/N-GPC catalyst shows a remarkably low overpotential of 9.6 mV (vs. RHE) at 10 mA/cm2, which is near ideal, providing 12 times faster hydrogen production rate than state-of-the-art Pt/C. We explain the atomistic basis for this low overpotential and superb stability via Grand canonical quantum mechanics calculations. These calculations show that pyrrolic-N in the support strengthens the coupling to the Ru NP while weakening the binding of H to Ru NP to accelerate the Tafel step.