Metal-phthalocyanine functionalized carbon nanotubes as catalyst for the oxygen reduction reaction: A theoretical study

Abstract

The covalent functionalization of metallic single-walled carbon nanotubes (CNTs) with transition metal phthalocyanines (MPc, with M=Mn, Fe and Co) are addressed by density functional calculations. The CNT–MPc catalytic activity toward the oxygen reduction reaction (ORR) is investigated through the O2 stretching frequency adsorbed on the phthalocyanine metal center. We find better reduction abilities when the CNT functionalization occurs through sp2-like bonds. Multiple stable-spin states for the M–O2 adduct are also found for M=Mn and Fe, suggesting higher ORR rates. The CNT–MPc complexes show metallic characteristics, suggesting favorable conditions to work as ORR cathode catalysts in fuel cells.