Gold Nanoparticles as the Catalyst of Single-Walled Carbon Nanotube Synthesis

Yoshikazu Homma

doi:10.3390/catal4010038

Abstract

Gold nanoparticles have been proven to act as efficient catalysts for chemical reactions, such as oxidation and hydrogen production. In this review we focus on a different aspect of the catalysis of gold nanoparticles; single-walled carbon nanotube (SWCNT) synthesis. This is not a traditional meaning of catalytic reaction, but SWCNTs cannot be synthesized without nanoparticles. Previously, gold was considered as unsuitable metal species as the catalyst of SWCNT synthesis. However, gold nanoparticles with diameters smaller than 5 nm were found to effectively produce SWCNTs. We discuss the catalysis of gold and related metals for SWCNT synthesis in comparison with conventional catalysts, such as iron, cobalt, and nickel.

Highlights

Graphene is a monolayer material composed of six membered rings of sp2 hybridized carbon atoms [1]
A single walled carbon nanotube (SWCNT) is a nano-scale cylinder composed of rolled-up graphene [1,2]
We focus on SWCNT synthesis by chemical vapor deposition (CVD) with Au and related metal catalysts

Summary

Introduction

Graphene is a monolayer material composed of six membered rings of sp hybridized carbon atoms [1]. Formation of the cylindrical structure of SWCNT requires a nanoparticle of, in most cases, metals Those metals, used for graphene and SWCNT synthesis, are called catalysts, especially in the case of SWCNTs. Catalyst species mostly used for SWCNT synthesis are iron-group metals; iron (Fe), cobalt (Co), and nickel (Ni) [4], which have been known to have a catalytic function to assist carbon feedstock cracking and produce graphite layer on the bulk material surface [5]. Catalyst species mostly used for SWCNT synthesis are iron-group metals; iron (Fe), cobalt (Co), and nickel (Ni) [4], which have been known to have a catalytic function to assist carbon feedstock cracking and produce graphite layer on the bulk material surface [5] For these species, a widely-accepted growth model is based on the vapor-liquid-solid (VLS) mechanism as the analogy of semiconductor nanowire growth from gold eutectic alloy [6,7]. The SWCNT growth is compared with those using conventional metal catalysts and the growth mechanism and controlled growth of SWCNTs are reviewed

SWCNT Synthesis

SWCNT Growth Mechanism from Gold Nanoparticles

Toward the Chirality Control

Comparison with Graphene Synthesis

Summary