Molecule-Assisted Synthesis of Highly Dispersed Ultrasmall RuO2 Nanoparticles on Nitrogen-Doped Carbon Matrix as Ultraefficient Bifunctional Electrocatalysts for Overall Water Splitting

Facile synthesis of ultrasmall metal-based materials as highly efficient bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of vital importance to energy storage and conversion technologies. Here, a novel molecule-assisted strategy for synthesis of ultrasmall ruthenium oxide on nitrogen-doped carbon matrix catalyst (RuO2/N–C) is presented. 1,10-Phenanthroline molecular (Phen), which contains an abundant nitrogen element and can strongly coordinate with metal ions, is selected as the assistant to prepare RuO2/N–C. The space confinement effect in this process gives RuO2 nanoparticles (NPs) with size ca. 1.7 nm, making them ultraefficient bifunctional electrocatalysts for both HER and OER. The resultant RuO2/N–C catalyst exhibits striking catalytic performances in strong alkaline solution, affording a current density of 10 mA cm–2 at low overpotentials of 40 mV for HER and 280 mV for OER, respectively. Experimental results and density functional theory (DFT) calculations reveal that the excellent performances are due to the ultrasmall size of RuO2 NPs and the synergistic effect between RuO2 and N–C. More importantly, these RuO2/N–C composites can be utilized as bifunctional electrocatalysts as both anode and cathode and display superior water splitting activity to that of the commercial Pt/C and RuO2 catalysts couple, suggesting the potential applications of our catalyst for large-scale H2 and O2 production in the future.