Arabian Journal for Science and Engineering https://doi.org/10.1007/s13369-020-04866-z RESEARCH ARTICLE-CHEMISTRY Heteroatoms (N, F, O)-Doped CNTs on NiCo-Silica Nanocomposites for Oxygen Evolution Reaction Zulfiqar Ali 1 · Mazhar Mehmood 1 · Jamil Ahmad 1 · Sumaira Naz 2 · Yaqoob Khan 3 Received: 1 April 2020 / Accepted: 13 August 2020 © King Fahd University of Petroleum & Minerals 2020 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/cm 2 , which was better than many reported carbonaceous materials in alkaline media. Keywords CNTs · OER · CVD · Alcogel electrolysis · NiCo-silica nanocomposites 1 Introduction Increasing clean energy demand has triggered the research activities for the production of hydrogen gas as a sustainable energy source through electrochemical water splitting [1–3]. The production of hydrogen in alkaline water electrolysers is well-established technology and it employs noble metals like iridium and platinum-based materials as electrodes for effi- cient water splitting process [4, 5]. Since noble metal-based electrocatalytic materials suffer from drawback of scarcity, B Zulfiqar Ali zulfiqarali_15@pieas.edu.pk 1 National Centre for Nanotechnology, Department of Metallurgy and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650, Pakistan 2 Materials Division, Directorate of Technology, Pakistan Institute of Nuclear Science and Technology (PINSTECH), Nilore, Islamabad 45650, Pakistan 3 Nanosciences and Catalysis Division, National Centre for Physics, Quaid-i-Azam University Campus, Islamabad, Pakistan high price and stability issues. Therefore, development of alternatives to replace the noble metal-based electrocatalysts is desirable [6, 7]. In this regard, particularly the oxygen evolution reaction (OER) in electrochemical water splitting process requires more attention due to sluggish kinetics and large overpotentials [8–11]. Developing efficient OER elec- trocatalyst materials is therefore urgently required. Many materials and strategies have been proposed by researcher across the globe. The non-carbon first-row transition metal, like (Ni, Co, Fe)-based OER electrocatalyst has been much explored for better OER activity, for instance; Chen et al. [12] developed ultrathin nickel film on FTO substrate through electrodeposition for water oxidation. Jin et al. [13] syn- thesized 3D Ni-Co phosphide core shell nanostructure for efficient OER activity. Zhang et al. [14] have produced CoSe 2 nanomeshes by plasma exfoliation technique with abundant active site OER catalysts. Although many transition metals- based OER electrocatalysts show low overpotentials but the main issue associated with these metal phosphide, selenides and oxides electrocatalysts is of low electrical conductivity and current density [15]. To overcome this problem car- bon nanostructured materials have been incorporated into 123