Carbon-supported palladium–polypyrrole Pd–PPy/C nanocomposite was synthesized by oxidative polymerization of pyrrole and
reduction of palladium(II) precursor salt in the presence of Vulcan XC-72R. The Pd–PPy/C composites were characterized by
X-ray diffraction (XRD), Fourier transform IR, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and
transmission electron microscopy (TEM) techniques. The XRD analysis of Pd–PPy/C shows the formation of the face-centered
cubic structure of Pd particles and the mean particle size calculated from TEM was 5.3 2.0 nm. The electrochemical stability
of Pd–PPy/C was examined by cyclic voltammetry in an acid solution. The thermal stability and Pd loading in the composite was
assessed using TGA. The introduction of Pd in the conducting PPy/C matrix gives better catalytic activity toward oxygen
reduction with resistance to methanol oxidation. This was further elucidated by the XPS analysis showing d-band vacancy that is
attributed to metal–polymer interaction. From the polarization studies, it is observed that even in the presence of methanol there
is no significant cathodic shift in the half-wave potential, revealing that Pd–PPy/C is tolerant to methanol. Rotating ring disk
electrode studies show that there is only a negligible quantity of hydrogen peroxide produced in the potential region where its
production is expected to be high. This confirms that Pd–PPy/C catalyzes reduction of oxygen directly to water through a
four-electron pathway
