Nanosheet-Derived Ultrafine CoRuOx@NC Nanoparticles with a Core@Shell Structure as Bifunctional Electrocatalysts for Electrochemical Water Splitting with High Current Density or Low Power Input

A series of ultrafine core@shell electrocatalysts (CoRuOx@NC) are prepared using oleylamine (OA)-passivated metal-oxide nanosheets (CoRuOy@OA) as single precursors. The optimal catalyst Co0.8Ru0.2Ox@NC composed of the N-doped carbon (NC) shell and the endohedral hybrid of metal/metal oxide exhibits excellent catalytic activities in alkaline media with a low overpotential of 36 mV for hydrogen evolution reaction, 278 mV for oxygen evolution reaction, and an ultralow potential of −19 mV for hydrazine oxidation reaction (HzOR) at 10 mA cm–2. When used as both cathode and anode catalysts for overall water splitting, Co0.8Ru0.2Ox@NC drives 10/500 mA cm–2 with a cell voltage as low as 1.55/1.86 V and maintains long-term stability at 500 mA cm–2. Moreover, for HzOR-assisted electrochemical water splitting (EWS), the Co0.8Ru0.2Ox@NC-based electrode couple requires ultralow cell voltages of merely 79/674 mV to deliver 10/100 mA cm–2 with excellent long-term durability at 100 mA cm–2. The success of the present electrocatalyst shall be attributed to the combined effect of minor RuOx incorporation and carbon encapsulation, which results in not only enhanced catalyst conductivity and charge transfer kinetics but also surface-enriched active sites and improved intrinsic catalytic activity. Thus, our work may pave a new opportunity for rational design and facile synthesis of bifunctional electrocatalysts for EWS operated with high current density or low power input.