Electrocatalytic reactivity for oxygen reduction of palladium-modified carbon nanotubes synthesized in supercritical fluid

The electrocatalytic reactivity of palladium-modified carbon nanotubes (Pd-CNTs) for the oxygen reduction reaction (ORR) was investigated at the glassy carbon electrode surface in 1 M H2SO4 saturated by oxygen. Carbon nanotubes modified by palladium nanoparticles were synthesized in supercritical carbon dioxide and characterized by transmission electron micrograph. The electrocatalytic activity of the CNTs film and Pd-CNTs film toward oxygen reduction was studied using cyclic voltammetry and linear sweep voltammetry methods. The molecular oxygen reduction at the Pd-CNTs electrode started at a more positive potential than that at the CNTs electrode. A possible reaction mechanism was proposed in which the ORR may proceed through two-step two-electron processes for the Pd-CNTs modified electrode. Experimental results revealed that Pd-CNTs possess a remarkable activity and high stability for oxygen reduction in acid medium, which implies the potential applications of the Pd-CNTs for constructing electrodes of fuel cells.