<b>Effect of reduction reaction on graphene-based support materials for palladium catalyst in direct methanol fuel cell</b><b></b>

Abstract

Palladium (Pd) catalyst supported by graphene support materials have been synthesized in this study. The graphene oxides (GO) and their reduced counterparts were obtained through modified hummer’s method and thermal reduction using hydrazine hydrate, respectively which were further doped with nitrogen using hydrazine. The catalysts were synthesized using modified polyol method. The structures were examined using FTIR and XRD for the support and prepared electrocatalysts respectively. The FTIR showed that the support materials exhibit oxygen containing functional groups which serve as the anchor sites for metal deposition while the XRD confirmed face-centered crystal structure of Pd catalyst. HR-TEM image showed spherical and agglomerated Pd nanoparticles dispersed on the support materials. The surface area of the support materials is analyzed using BET Technique. Reduced graphene oxide (rGO) showed the highest surface area followed by Nitrogen-doped graphene oxide (N-rGO) compared to other prepared support materials. ICP-OES was used to estimate the Pd concentration and was observed to be closest to that of commercial, Vulcan XC-72. The electrochemical evaluation of the synthesized electrocatalysts revealed that Pd/rGO and Pd/N-rGO exhibit the highest activity towards methanol oxidation with Pd/rGO as the best. These enhanced activities in Pd/rGO and Pd/N-rGO can be ascribed to the reduction of GO to rGO with a notable increase in carbon to oxygen atomic ratio which increases the electroactive surface area of rGO and N-rGO support materials and also enhance the synergistic interaction between the Pd nanoparticles and the support materials.