Heteroatoms (N, F, O)-Doped CNTs on NiCo-Silica Nanocomposites for Oxygen Evolution Reaction

Abstract

The more electronegative atoms of element like nitrogen, fluorine and oxygen in CNTs are highly desirable for electrochemical catalytic reactions like oxygen evolution reaction (OER). Herein, we report the synthesis of in situ nitrogen-doped CNTs by CVD method on fcc NiCo alloy-silica nanocomposites in ethylene precursor containing 10% acetonitrile and their catalytic behaviour for oxygen evolution in alkaline media. The XPS analysis revealed that about 2 atomic% nitrogen was successfully doped in CNTs. Although the amount of doped nitrogen was not substantial, it played a significant role in the formation of bamboo-shaped CNTs by facilitating the conical shape of nanocatalyst. The internal core of the CNTs was analysed by TEM studies and it was found that CNTs have irregular cup and cone compartments repeated at a distance of about 50 nm. The oxygenated functional groups in the form of C=O and O–F were also found which owe their presence on the surface of CNTs to the aqueous HF treatment. The unique features like the presence of heteroatoms (N, F, O) at the graphitic planes of CNTs and its bamboo shape have collectively improved the OER performance of our synthesised carbonaceous material. As a result it exhibited OER overpotential of 315 mV at current density of 10 mA/cm2, which was better than many reported carbonaceous materials in alkaline media.