Synthesis and characterization of metal nanoparticles-decorated PPY-CNT composite and their electrocatalytic oxidation of formic acid and formaldehyde for fuel cell applications

Polymer composite films encompassed of polypyrrole (PPY) and multi-walled carbon nanotubes (MWCNT) [PPY-CNT] were synthesized by in situ polymerization of pyrrole on carbon nanotubes in 0.1 M HCl containing(NH4)S2O8 as oxidizing agent at 0-5 degrees C. 2-4 nm sized metal nanoparticles, viz. Pt and Pt-Pd were then deposited on the prepared polypyrrole/CNT composites by chemical reduction of the corresponding metal salts using HCHO as reducing agent at pH 11. The fabricated nanoparticles-decorated composite films were then used as a probe towards formic acid and formaldehyde oxidation. Furthermore, the addition of CNT to polypyrrole imparts a high activity, which might be due to the higher electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/carbon nanotubes interfaces allowing a higher dispersion and utilization of deposited Pt and Pt-Pd nanoparticles. Results from formic acid and formaldehyde oxidation showed that Pt-Pd nanoparticles-modified Ppy-CNT exhibits better catalytic activity and stability in contrast to Pt supported on Ppy-CNT. Pt and Pt-Pd nanoparticles are found homogeneously dispersed in Ppy-MWCNT composites ascertained from various analytical data like scanning electron microscopy (SEM), transmission electron microscopy ITEM). Energy dispersive X-ray analysis (EDAX) is used to characterize the nature of metal present in the nanoparticles-modified electrodes. (c) 2007 Elsevier B.V. All rights reserved.