Controllable fabrication of graphitic nanocarbon encapsulating FexNiy hybrids for efficient splitting of water

The hybridized electrocatalysts constituted by binary 3d transition nanoparticles with a varied ratio of Fe to Ni were successfully synthesized through a two-step fabrication procedure, a homogeneous precipitation process, and a successive graphitization process. A superior oxygen evolution reaction (OER) efficiency with a yielded remarkable low overpotential of ∼0.26 V and a Tafel slope of ∼56 mV/decade is achieved for the heterostructured Fe1Ni2 nanoparticles coated by graphitic nanocarbon in a 1 mol/L KOH solution. The influencing factors for synthesizing the electrocatalysts, such as the graphitization temperature, the content of iron and the thickness of the carbon shells are also carefully investigated, and improved electrocatalytic efficiency is achieved with appropriate fabrication parameters for the hybridized catalysts. It is considered that the synergistic effect of the defects and electrochemical conductivity of the graphitic carbon shells shows great influences on the electrocatalytic activity. In addition, the detailed electrochemically active surface area and the electrochemical impedance suggest that the FexNiy hybrids coated by graphitic nanocarbon have improved the mass transport and electron transfer rate, resulting in an enhanced electrocatalytic water splitting efficiency. This work opens up a new way to fabricate promising oxygen-evolving catalysts with high-efficiency and low-cost.