Electrocatalysis of oxygen reduction on multi-walled carbon nanotube supported Ru-based catalysts in alkaline media

Ru and bimetallic Ru-M (M = Ni and Sn) nanoparticles were supported on the multi-walled carbon nanotubes (MWCNTs) and Vulcan carbon (XC-72). Morphology of nanoparticles was investigated by scanning electron microscopy (SEM). The kinetics and mechanism of the oxygen reduction reaction (ORR) were analyzed in 0.1 M NaOH solution. From rotating disk electrode (RDE) studies, it was found that the number of electrons (n) involved in the ORR depends on the alloy compositions. For single Ru nanoparticles, n was 2 and for alloy nanoparticles the value of n increases almost to 4. The number of electrons transferred was calculated 3.88 for Ru Ni/MWCNTs. The prepared nanoparticles were used as the active catalyst of gas diffusion electrodes (GDEs). The electrocatalytic performance of the GDEs was investigated by cyclic voltammetery (CV), AC impedance spectroscopy (EIS) and chronoamperometery methods. The Ru Ni/MWCNs indicated the lowest charge transfer resistance in the whole range of applied potentials. According to the electrochemical measurements, the Ru-WMWCNT catalysts displayed significantly higher performance than the Ru-WC catalysts. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.