Effect of pyrolysis temperature on cobalt phthalocyanine supported on carbon nanotubes for oxygen reduction reaction
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Cobalt phthalocyanine (CoPc)-impregnated functionalized multi-walled carbon nanotubes (CNTs) were used as nonprecious electrocatalysts for oxygen reduction reaction (ORR). The electrocatalysts were thermally treated at temperatures ranging from 450 to 850 °C, and the effect of pyrolysis temperature and their relationship to the electrocatalytic activity for ORR were investigated. Thermo gravimetric analysis, X-ray diffraction, and electron microscopy were used to study the thermal stability, crystal structure, and morphology of these catalysts. Cyclic voltammetry and rotating disk electrode results showed that CoPc/CNTs pyrolyzed at a temperature of 550 °C had the highest electrocatalytic activity for ORR, and the catalytic activity decreased with further increase in pyrolysis temperature. X-ray photoelectron spectroscopy showed decrease in functional groups at a temperature higher than 550 °C, correlating with the decreased catalytic activity. The result suggests that oxygen functional groups introduced by acid oxidation for anchoring the CoPc on CNT plays a major role in determining the electrocatalytic activity.
KeywordsOxygen reduction reaction Carbon nanotubes Cobalt phthalocyanine Cathode catalyst Fuel cells
The authors’ sincere thanks go to the Industrial Consultancy and Sponsored Research (IC & SR) and the Department of Chemical Engineering, Indian Institute of Technology (IIT) Madras for the financial support under the New Faculty Scheme. The authors also thank the staff members of the Sophisticated Analytical Instrument Facility (SAIF) at IIT Madras for their assistance with the physical characterization.
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