Ruthenium Ion-Complexed Graphitic Carbon Nitride Nanosheets Supported on Reduced Graphene Oxide as High-Performance Catalysts for Electrochemical Hydrogen Evolution

Carbon-based materials are promising, low-cost electrocatalysts toward hydrogen evolution reaction (HER), although the catalytic performance needs to be further improved before commercialization. In this study, ruthenium ions are incorporated into graphitic carbon nitride/reduced graphene oxide (rGO) hybrids to form Ru-C₃ N₄ /rGO composites through Ru-N coordination bonds. The incorporation of Ru ions, at a loading of 1.93 at. %, leads to electron redistribution within the materials and dramatically enhances the HER performance over those of C₃ N₄ , C₃ N₄ /rGO, and Ru-C₃ N₄ , with an overpotential of only -80 mV to reach a current density of 10 mA cm^-2 , a Tafel slope of 55 mV dec^-1 , and an exchange current density of 0.462 mA cm^-2 . This performance is comparable to that of Pt/C, and ascribed to the positive shift of the conduction band of the composite, where the charge carrier density increases by a factor of about 250 over that of C₃ N₄ , leading to a lower energy barrier for hydrogen evolution. The results suggest a new strategy in the design and engineering of functional nanocomposites for effective HER electrocatalysis by embedding select metal ions into carbon-based molecular skeletons.