Electrochemical performance of carbon nanotube-supported cobalt phthalocyanine and its nitrogen-rich derivatives for oxygen reduction

Multiwalled carbon nanotube (MWCNT)-supported cobalt phthalocyanine (CoPc), cobalt tetrapyridinoporphyrazine (CoTAP), and cobalt tetrapyrazinoporphyrazine (CoPTpz) assemblies are prepared by solid phase synthesis method. The products are characterized by infrared spectroscopy, scanning and transmission electron microscopy and UV-vis spectroscopy. The electrocatalytic activity of the obtained MWCNT-supported CoPc, CoTAP and CoPTpz assemblies is measured by rotating disk electrode techniques and cyclic voltammetry in an oxygen-saturated 0.1 M KOH. The results show that MWCNT-supported CoPc shows a two-step, two-electron process for the reduction of oxygen reduction (ORR), whereas MWCNT-supported CoTAP and CoPTpz electrodes exhibit a one-step, four-electron pathway for ORR, indicating that N atoms in the backbone of the compounds strongly affect the catalytic activity of MWCNT-supported CoPc derivative assemblies. The MWCNT-supported CoTAP and CoPTpz assemblies have higher activity to oxygen reduction than that of MWCNT-supported CoPc attributed to their different catalytic mechanisms to ORR.