Facile synthesis of novel Pt–Ru@PPy–MWNT electrocatalysts for direct methanol fuel cells

Abstract

Pt–Ru@polymer–multiwall carbon nanotubes (MWNT) composites were successfully prepared as electrocatalysts by loading Pt–Ru nanoparticles onto the surface of polymer coated-MWNT. Polymers such as poly(β-caprolactone), poly(maleic anhydride), and poly(pyrrole). Polymer coating on the surface of MWNT was performed by in situ polymerization of the respective monomer in the presence of MWNT. Pt–Ru nanoparticles were deposited onto polymer–MWNT composite by the reduction of the metal ions (Pt 4+ and Ru 3+) using γ-irradiation. Thus, Pt–Ru@polymer–MWNT catalysts were obtained. The Pt–Ru@polymer–MWNT catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD) and elemental analysis for morphology, size and composition, respectively. The polymer was found to be coated to a thickness of 5–35 nm over the surface of MWNT. TEM images of the Pt–Ru@polymer–MWNT composite indicates that Pt–Ru alloy nanoparticles are more dispersed on the surface of polymer–MWNT composites as compared to the surface of pristine MWNT. The surface of polymer–MWNT is changed to hydrophilic as compared to the hydrophobic surface of pristine MWNT. The catalytic efficiency of Pt–Ru@polymer–MWNT catalyst was examined for the oxidation of carbon monoxide (CO) and methanol. The electrodes fabricated with Pt–Ru@PPy–MWNT and Pt–Ru@PMA–MWNT show enhanced activity for the electro-oxidation of methanol over the Pt–Ru@PCL–MWNT electrode. Also, results from stripping voltammetry for the adsorbed CO at Pt–Ru@polymer–MWNT catalyst electrodes inform that CO oxidation is energetically favorable at these electrodes. Thus, Pt–Ru@polymer–MWNT catalysts are suited for the electrode assembly in direct methanol fuel cells.