Herein, we report in-situ NiCo alloy nanoparticle formation of extremely small diameter (1-5 nm) on nitrogen (N)-doped carbon spheres by the CVD method at 750 °C temperature, followed by its use in oxygen evolution reaction (OER) electrocatalysis. Secondary electron microscope (SEM) imaging shows the open as well as close cup-shaped spheres and discs, while transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies confirmed the ultrafine NiCo alloy particles' formation on nitrogen-doped multilayer graphitized carbon. Moreover, Raman spectroscopy revealed the I D /I G ratio to be about 1.57 for N-doped graphitic multilayer carbon, thereby suggesting the defective nature of graphitized carbon material, which may possibly be due to the incorporation of nitrogen atoms into graphitic carbon layers. The formation of extremely small NiCo alloy nanoparticles is attributed to the reducing carbonaceous environment of CVD constituted by ethanol and acetonitrile precursors, while carbon spheres/disks seem to be catalysed by silica substrate originated from an alcogel catalyst. In addition, synthesised hybrid nanocomposites materials were tested for OER electrocatalysis in alkaline conditions and it was found that synthesized NiCo alloy nanoparticles decorated on N-doped carbon spheres have an overpotential 310 mV at current density of 10 mA/cm 2 which is just 5 mV higher than that of benchmark Ir/C (20 wt % Ir) electrocatalyst. The multiphase components of synthesised material like; electrically conductive carbon, nitrogen-doped sites and well-separated ultrafine NiCo alloy nanoparticles synergistically contributed towards better OER activity in alkaline conditions.

Carbon nanostructures with a high‐density of active sites are needed as catalysts for the oxygen evolution reaction (OER). Here we report a platelet graphitic nanofiber‐carbon nanotube (PGNF‐CNT) hybrid electrocatalyst prepared by chemical vapor deposition. The material is composed of interconnected CNTs and nanofibers consisting of graphitized carbon layers stacked at different angles to the fiber axis with a large number of exposed edges. These unique structural characteristics give the hybrid a high density of active sites, fast electron transfer and a large number of mass transport paths. As a result, the material has an excellent electrocatalytic activity for OER with an overpotential of 0.28 V at a current density of 10 mA cm−2, which is much better than those of Ir/C and previously‐reported carbonaceous catalysts.

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