Synthesis of Nitrogen-Doped Carbon Nanotubes Using Injection-Vertical Chemical Vapor Deposition: Effects of Synthesis Parameters on the Nitrogen Content

Abdouelilah Hachimi,Qiaowan Chang,Abbas Hakeem,Muataz Ali Atieh,Greg M Swain,Minhua Shao,Belabbes Merzougui,Tahar Laoui

doi:10.1155/2015/453725

Abstract

Nitrogen-doped CNTs (N-CNTs) were synthesized using an injection-vertical chemical vapor deposition (IV-CVD) reactor. This type of reactor is quite useful for the continuous mass production of CNTs. In this work, the optimum deposition conditions for maximizing the incorporation of nitrogen were identified. Ferrocene served as the source of the Fe catalyst and was dissolved in acetonitrile, which served as both the hydrocarbon and nitrogen sources. Different concentrations of ferrocene in acetonitrile were introduced into the top of a vertically aligned reactor at a constant flow rate with hydrogen serving as the carrier. The effects of hydrogen flow rate, growth temperature, and catalyst loading (Fe from the ferrocene) on the microstructure, elemental composition, and yield of N-CNTs were investigated. The N-CNTs possessed a bamboo-like microstructure with a nitrogen doping level as high as 14 at.% when using 2.5 to 5 mg/mL of the ferrocene/acetonitrile mixture at 800°C under a 1000 sccm flow of hydrogen. A production rate of 100 mg/h was achieved under the optimized synthesis conditions.

Highlights

CNTs and nitrogen-doped CNTs as emerging materials for many applications can be synthesized by many methods, such as arc-discharge, laser ablation, spray pyrolysis, and chemical vapor deposition (CVD)
Cracking or decomposition of the ACN and FcH leads to the formation of free radicals, which are transported to the Fe catalyst sites where they adsorb and react to grow nitrogen-doped carbon nanotubes (N-CNTs) [26]
Nitrogen-doped carbon nanotubes were synthesized using a mixture of FcH and ACN in an inverted-vertical CVD reactor

Summary

Introduction

CNTs and nitrogen-doped CNTs as emerging materials for many applications can be synthesized by many methods, such as arc-discharge, laser ablation, spray pyrolysis, and chemical vapor deposition (CVD). Horizontally aligned CVD reactors have been used to produce carbon materials in variety of forms including aligned or entangled, straight or coiled, and even a desired architecture of nanotubes at predefined sites on a patterned substrate with high purity but with low yield (few grams) [6, 7]. Aligned CVD reactors with different synthesis mechanisms have been used to produce large quantities in the order of kg/h [8,9,10,11,12,13]. Great attentions have been devoted to the study of nitrogen-doped carbon nanotubes (N-CNTs) because of their excellent properties, especially the electrical conductivity and electrocatalytic activity for oxygen reduction reaction [1, 2, 14,15,16,17,18,19,20,21,22]

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