Catalytic activity of polypyrrole nanotubes decorated with noble-metal nanoparticles and their conversion to carbonized analogues

Abstract

Polypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in the presence of methyl orange. They were subsequently used as a substrate for the reductive deposition of noble metal particles. Polypyrrole nanotubes decorated with palladium, platinum, rhodium, or ruthenium nanoparticles were characterized by electron microscopy, conductivity, energy dispersive X-ray analysis, and FTIR and Raman spectroscopies. A typical metal content varied between 15 and 20wt.%. The catalytic activity of composites was illustrated on the reduction of 4-nitrophenol to 4-aminophenol. The carbonization of composites has been followed by thermogravimetric analysis in nitrogen atmosphere. The nanotubular morphology of polypyrrole was retained after carbonization up to 830°C. The noble-metal nanoparticles, nanometres in size, fused to clusters during this process, except for ruthenium. Polypyrrole nanotubes were converted to a nitrogen-containing carbon and platinum nanoparticles still preserved during carbonization at 400–500°C.