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 °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 (TEM). Energy dispersive X-ray analysis (EDAX) is used to characterize the nature of metal present in the nanoparticles-modified electrodes.