Poly(3-hexylthiophene)-multi-walled carbon nanotube (1:1) hybrids: Structure and electrochemical properties

Two types of poly(3-hexylthiophene)-multi-walled carbon nanotubes (MWCNT) hybrids were prepared and their electrochemical properties were compared. A dispersion of MWCNT modified with monomeric thiophene derivative (MWCNT-thio) and the monomer 3-hexylthiophene (3HT) were allowed to react by in-situ oxidative polymerization to prepare a P3HTMWCNT covalent hybrid. The hybrid was synthesized with a 1:1 (polymer:MWCNTs) mass ratio and was easily dispersed in common organic solvents. Moreover, a second type of hybrid was obtained by polymerization of 3HT in the presence of MWCNT amine-functionalized with the same component ratio (non-covalent hybrid P3HT/MWCNT). The covalent hybrid (P3HTMWCNT) achieved an electrical conductivity of 4.6 × 10−1 S cm−1, which was 5 times higher than that of the hybrid produced with polymer adsorption on the MWCNT. This result provides a strong evidence of enhancement in charge transfer by covalent attachment between polymer and nanotubes. The chemical structure and morphology of the hybrids were compared with those of neat P3HT and neat MWCNTs. Moreover, the covalent hybrid was used as an electrode in a pseudocapacitor with an organic liquid electrolyte and this device was compared to a supercapacitor based only in electrodes of MWCNT (pure double layer capacitance). The device showed high performance with a specific capacitance of 239 F g−1 at a current density of 3 A g−1, which is 585% higher than the supercapacitor based on MWCNT electrodes at 1 A g−1 (maximum current obtained). The results presented here demonstrating that a carbon nanotube-conjugated polymer hybrid with equivalent content of the components covalently linked can be a better choice for application in electrodes than the counterparts with adsorpted polymer or composites with polymer in excess.