Single-Step Synthesis of Vertically Aligned Carbon Nanotube Forest on Aluminium Foils.

Fabien Nassoy,Thomas Goislard De Monsabert,Pierre-Henri Aubert,Philippe Banet,Mathieu Pinault,Harald Hauf,Martine Mayne-L’Hermite,Thomas Vignal,Jérémie Descarpentries,Pierre-Eugène Coulon,Cécile Reynaud

doi:10.3390/nano9111590

Abstract

Vertically aligned carbon nanotube (VACNT) forests are promising for supercapacitor electrodes, but their industrialisation requires a large-scale cost-effective synthesis process suitable to commercial aluminium (Al) foils, namely by operating at a low temperature (<660 °C). We show that Aerosol-Assisted Catalytic Chemical Vapour Deposition (CCVD), a single-step roll-to-roll compatible process, can be optimised to meet this industrial requirement. With ferrocene as a catalyst precursor, acetylene as a carbon source and Ar/H2 as a carrier gas, clean and dense forests of VACNTs of about 10 nm in diameter are obtained at 615 °C with a growth rate up to 5 µm/min. Such novel potentiality of this one-step CCVD process is at the state-of-the-art of the multi-step assisted CCVD processes. To produce thick samples, long synthesis durations are required, but growth saturation occurs that is not associated with a diffusion phenomenon of iron in aluminium substrate. Sequential syntheses show that the saturation trend fits a model of catalytic nanoparticle deactivation that can be limited by decreasing acetylene flow, thus obtaining sample thickness up to 200 µm. Cyclic voltammetry measurements on binder-free VACNT/Al electrodes show that the CNT surface is fully accessible to the ionic liquid electrolyte, even in these dense VACNT forests.

Highlights

Energy storage is a major challenge for the development of renewable energies, mobile devices and electric vehicles
Vertically Aligned Carbon Nanotube (VACNT) are synthesized on aluminium substrates through the aerosol-assisted Chemical Vapour Deposition (CCVD) process, operated at atmospheric pressure in an experimental set-up (Figure S1 in Supplementary Materials) adapted from those described previously [21,31,32]
The one-step aerosol-assisted CCVD process was successfully optimized at a low temperature in order to produce VACNT forest on aluminium foils with a competitive growth rate, paving the way for its industrial development

Summary

Introduction

Energy storage is a major challenge for the development of renewable energies, mobile devices and electric vehicles In this context, supercapacitors, based on rapid ion charge/discharge cycles, have great potential, with performance between capacitors and batteries [1]. Its specific capacitance (SC) does not increase linearly with its SSA due to a too-large pore size distribution, in which the narrowest pores are not accessible to solvated ions [2]. It suffers from a slow diffusion kinetics of the electrolyte in the porosities and a poor electrical contact with the current collector [3]. The direct growth of VACNT on Al foils at a relatively low cost through a scalable process must be developed to obtain competitive electrodes for supercapacitors

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Conclusion