Modification of multi-walled carbon nanotubes with cobalt phthalocyanine: effects of the templates on the assemblies

Abstract

Cobalt phthalocyanine (CoPc) assemblies are prepared using several kinds of multiwalled carbon nanotube (MWCNT) templates by in situ solid synthesis in a muffle furnace. The products are characterized by infrared spectroscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and differential thermal analysis-thermogravimetry. The electrocatalytic activity of the obtained MWCNT-templated CoPc assemblies is measured by cyclic voltammograms in an oxygen-saturated 0.5 M H₂SO₄. The results show that the CoPc assemblies have several different structures: CoPc nanothreads supported by MWCNTs, nanocrystals mixed with MWCNTs and CoPc/MWCNT coaxial nanotubes. The size and the structure of CoPc assemblies are controlled by the interfacial interaction, including π–π interaction, hydrogen bond and coordinate bond, between CoPc and the MWCNTs, which strongly depend on the microstructure of the MWCNTs. Thermal analysis shows CoPc/MWCNT coaxial nanotubes exhibit higher thermal stability than the assemblies with the structure of CoPc nanothreads supported by MWCNTs and nanocrystals linked to MWCNTs. In addition, the cyclic voltammogram measurements show they display different electrochemical characteristics depending on their structures. CoPc/MWCNT assemblies with coaxial nanotube structure have better electrocatalytic activity to oxygen reduction than the others.