Optimization of the Pd-Sn-GNS nanocomposite for enhanced electrooxidation of methanol

Highly dispersed Pd nanoparticles with varying loadings (15-40 wt%) and (20 - x)%Pd-x% Sn (where x = 1, 2, 3 and 5) nanocomposites are obtained on graphene nanosheets (GNS) by a microwave-assisted ethylene glycol (EG) reduction method for methanol electrooxidation in alkaline solution. The electrocatalysts were characterized by XRD, SEM, TEM, cyclic voltammetry, and chronoamperometry. The study shows that the Pd nanoparticles on GNS are crystalline and follow the face centered cubic structure. Introduction of a small amount of Sn (1-5 wt%) shifts the characteristic diffraction peaks for Pd slightly to a lower angle. The electrocatalytic performance of the Pd/GNS electrodes has been observed to be the best with 20 wt% Pd loading; a higher or lower loading than 20 wt% Pd produces an electrode with relatively low catalytic activity. The apparent catalytic activity of this active electrode at E = -0.10 V is found to improve further by 79% and CO poisoning tolerance by 40% with introduction of 2 wt% Sn. Among the electrodes investigated, the 18%Pd-2%Sn/GNS exhibited the greatest electrocatalytic activity toward methanol electrooxidation. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.