Coral-like carbon-wrapped NiCo alloys derived by emulsion aggregation strategy for efficient oxygen evolution reaction.

ABSTRACT

The transition metal-based catalysts have great potential to boost the electrocatalytic reactions due to their flexible electronic configuration and low cost. This work developed a facile emulsion aggregation strategy to synthesize coral-like carbon-wrapped NiCo alloy (Co0.5Ni0.5/rGO) with high oxygen evolution reaction (OER) activity. The effect of alloy composition and GO content on the OER activity was evaluated in the 1 mol L-1 KOH solution. The OER mechanism of the Co0.5Ni0.5/rGO catalyst was disclosed by X-ray photoelectron spectra (XPS) and synchrotron radiation X-ray absorption spectra (XAS). The emulsion containing amphipathic graphene oxide (GO) and hydrophobic nickel/cobalt complexes induces the formation of the carbon-wrapped nanostructure. The coral-like Co0.5Ni0.5/rGO catalyst exhibits the low overpotential of 288 mV at the current density of 10 mA cm-2 and good durability, both of which are superior to the standard RuO2. The synergistic effect between nickel and cobalt effectively regulates the electronic structure and OER activity of the alloy catalysts. Moreover, the interaction between NiCo alloys and carbon shells can reduce the interfacial resistance.