The coupling of metallophthalocyanine with carbon nanotubes to produce a nanomaterial-based catalyst for reaction-controlled interfacial catalysis

A nanomaterial-based metallophthalocyanine catalyst (CoTAPc-MWCNTs) was prepared by covalently immobilizing cobalt tetraaminophthalocyanine (CoTAPc) on multiwalled carbon nanotubes (MWCNTs). The decomposition reaction of H2O2 was chosen to investigate the coupled catalytic performance. The results of electron paramagnetic resonance and online electrochemical experiments indicated that the catalytic mechanism of CoTAPc-MWCNTs is different from that of cobalt phthalocyanine molecular catalysts. The catalytic pathway of CoTAPc-MWCNTs involves the following steps: first, electron transfer from CoTAPc to H2O2 occurs through the coordination between the central cobalt ion and H2O2, reducing H2O2 to H2O; second, electrons are transferred from MWCNTs to the oxidized CoTAPc, forming hole-doped MWCNTs; finally, hole-doped MWCNTs accept electrons from H2O2, oxidizing H2O2 to O2. When using N,N-diethyl-1,4-phenylenediamine as a chromogenic substance, one obtained a quantitative estimate of holes injected in MWCNTs, corresponding to 1 hole for about 55 carbon atoms. Furthermore, CoTAPc-MWCNTs exhibit very unusual characteristics of controlled catalysis due to the special hydrophobic surface of the MWCNTs, and can be used as an interfacial catalyst for the determination of H2O2 concentration.