Preparation of Pd_xAu_y bimetallic nanostructures with controllable morphologies supported on reduced graphene oxide nanosheets and wrapped in a polypyrrole layer

In this paper, we have introduced a one-step method to prepare Pd_xAu_y bimetallic nanostructures supported on reduced graphene oxide (rGO) nanosheets and wrapped in a polypyrrole (PPy) layer. By using a pyrrole monomer as a special reducing agent for metal salts, the morphologies of Pd_xAu_y bimetallic nanostructures could be easily turned to be spherical, coral-like and porous cluster-like via simply changing dosage or molar ratio of PdCl₂ and HAuCl₄·4H₂O. The roles of the pyrrole monomer and rGO support in formation of rGO/Pd_xAu_y/PPy composites were investigated in detail. Transmission electron microscopy, elemental mapping analysis, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier-transform infrared spectra were used to characterize their morphologies, structures and compositions. Compared with corresponding rGO/Pd/PPy and rGO/Au/PPy composites, the as-prepared rGO/Pd_xAu_y/PPy composites displayed enhanced catalytic activity towards the reduction of 4-nitrophenol.