Green synthesis of N-doped MWCNTs via simple modification of CVD technique and evaluation of its viability as an electrode in AEMFC

Abstract

The conventional synthesis of multi-walled carbon nanotubes (MWCNT) presents an environmental challenge due to toxic precursors. This research proposes a green synthesis of MWCNT by chemical vapor deposition (CVD) using a natural carbon source precursor (olive oil). Nitrogen gas was used as an inert atmosphere and a carrier for the evaporator precursor (200 °C). MWCNTs were synthesized at 900 °C using NiCl2 as a catalyst. MWCNTs had two treatments: functionalized and purified with HNO3 and HCl. Different physicochemical techniques characterized the MWCNT, such as X-ray diffraction (XRD), FTIR, high-resolution transmission electron microscopy (HRTEM), XPS, Raman spectroscopy, and CHN-S. The size of the MWCNT grew to be between de 15 a 25 nm with a purity of 20%, while the Raman spectroscopy revealed structural changes in the MWCNT after the purification treatment due to variations in the ID/IG index. All the synthesized MWCNTs were electrochemically characterized with linear sweep and cyclical voltammetry to analyze their electrocatalytic response to oxygen reduction reaction (ORR) in alkaline media.