Raghuram Chetty

Multiwalled carbon nanotubes (CNTs) functionalized by oxygen plasma were used as a support for platinum-ruthenium nanoparticles for electrochemical methanol oxidation. The influence of plasma treatment time on the electrocatalytic activity was investigated by cyclic voltammetry, CO stripping voltammetry, and chronoamperometry. The electrocatalysts were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results showed that oxygen plasma treatment led to the formation of -CO and -COO groups on the CNT surface. Platinum-ruthenium nanoparticles dispersed with an optimum plasma treatment time of 30 min exhibited the maximum catalytic activity towards methanol oxidation. The rationale for the high catalytic activity is discussed.

Silver catalysts with three different metal loadings e.g. 10, 20 and 40wt% were synthesised on carbon nanotubes (Ag/CNT) support by glycerol reduction method. The catalysts were characterised by X-ray diffraction, electron microscopy and thermogravimetric analysis. The average crystalline size of Ag was found between 10 and 16nm for the metal loading from 10 to 40wt%. The catalytic activity towards oxygen reduction reaction (ORR) in alkaline solution was studied for the Ag/CNT catalysts in terms of mass activity as well as specific activity. Cyclic voltammetry and rotating disc electrode studies showed higher current density for 40wt% Ag/CNT catalyst, which maintained suitable durability in potential sweeping cycling in comparison to 10 and 20wt% Ag/CNT. The fuel cell studies of the synthesized catalysts were conducted using an anion exchange membrane, and all the three Ag/CNT catalysts showed open circuit voltage above 1V with 40wt% Ag/CNT gave the highest peak power density of 26.1mWcm-2 at room temperature, in good agreement with the kinetic data obtained from the half-cell studies.

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 amajor role in determining the electrocatalytic activity. © Springer Science+Business Media B.V. 2012.