Layer-by-layer spray deposition and unzipping of single-wall carbon nanotube-based thin film electrodes for electrochemical capacitors

Spray deposited single-wall carbon nanotube (SWCNT) film electrodes comprising a randomly interconnected meso-porous network with high electrical conductivity and ionic mobility when immersed in an electrolyte have been investigated for applications in electrochemical capacitors. Layer-by-layer (LbL) spray deposition assembly of functionalised, oppositely charged (carboxylic COO- or amine NH3+) SWCNTs has been used to control the density and structure of sprayed electrodes, followed by vacuum and hydrogen heat treatment, and their electrochemical performance as a supercapacitor electrode assessed. Sprayed LbL SWCNT electrodes had faster charging and discharging kinetics than SWCNT-COOH electrodes, with a capacitance of 94 F g(-1) compared with 63 F g(-1) at 2 mV s(-1) in a 1 M H2SO4 electrolyte; and LbL electrode capacitance was maintained to 91 F g(-1) at 200 mV s(-1). The capacitance of LbL SWCNT electrodes increased to 151 F g(-1) at 2 mV s(-1) after vacuum and H-2 heat treatment that removed NH2 and COOH functional groups, and resulted in a hybrid microstructure of SWCNTs and multi-layer graphene sheets from unzipped SWCNTs. (C) 2013 Elsevier Ltd. All rights reserved.