Effect of a Metallocene Catalyst Mixture on CNT Yield Using the FC-CVD Process

Devika Chauhan,Vesselin N. Shanov,Kinshuk Dasgupta,Guangqi Zhang,Anuptha Pujari,Mark J. Schulz

doi:10.3390/catal12030287

Abstract

This work studies synthesis of carbon nanotube (CNT) sheet using the high temperature (1400 °C) floating catalyst chemical vapor deposition (FC-CVD) method. Three metallocenes—ferrocene, nickelocene, cobaltocene—and their combinations are used as precursors for metal catalysts in the synthesis process. For the carbon source, an alcohol fuel, a combination of methanol and n-hexane (9:1), is used. First, the metallocenes were dissolved in the alcohol fuel. Then, the fuel mixture was injected into a tube furnace using an ultrasonic atomizer with Ar/H2 carrier gas in a ratio of about 12/1. The synthesis of CNTs from a combination of two or three metallocenes reduces the percentage of metal catalyst impurity in the CNT sheet. However, there is an increase in structural defects in the CNTs when using mixtures of two or three metallocenes as catalysts. Furthermore, the specific electrical conductivity of the CNT sheet was highest when using a mixture of ferrocene and cobaltocene as the catalyst. Overall, the multi-catalyst method described enables tailoring certain properties of the CNT sheet. However, the standard ferrocene catalyst seems most appropriate for large-scale manufacturing at the lowest cost.

Highlights

Since the discovery of carbon nanotubes (CNTs) by Iijima in 1991 [1], they have drawn the attention of researchers across the world
It should be noted that less than 0.1% of the supplied Fuel IV (Fe) catalyst contributes toward CNT growth [45] and the currently achieved carbon efficiency is 1–4% [46]
We investigate the effect of using a mixture of ferrocene, nickelocene, and cobaltocene catalysts coexisting in fuel to synthesize CNTs at high temperature (1400 ◦C) by the floating catalyst chemical vapor deposition (FC-chemical vapor deposition (CVD)) method

Summary

Introduction

Since the discovery of carbon nanotubes (CNTs) by Iijima in 1991 [1], they have drawn the attention of researchers across the world. We investigate the effect of using a mixture of ferrocene, nickelocene, and cobaltocene catalysts coexisting in fuel to synthesize CNTs at high temperature (1400 ◦C) by the FC-CVD method. Using a combination of metallocene for CNT synthesis in a horizontal tube, the FC-CVD method at a temperature of 1400 ◦C is an important study topic. We show continuous synthesis of the aerogel-like sock by mixing two and three metal catalysts in the fuel, along with the effect of using a metallocene mixture on the CNT yield. The floating catalyst method uses the pyrolysis process for (CNT) synthesis

II III

Calculation

Findings

Conclusions