Formation of CuPd and CuPt Bimetallic Nanotubes by Galvanic Replacement Reaction

A galvanic replacement reaction has been successfully applied to prepare CuPd and CuPt bimetallic nanotubes. The nanotubes were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) techniques. Ultralong, single crystalline copper nanowires (NWs) with a diameter of ∼64 nm and a length of several micrometers were used as template material. By controlling the amount of noble metal salt added, nanotubes with different compositions were obtained. After the replacement of Cu with Pt, nanotubes composed of a PtCu alloy were formed. EDS analysis revealed that the Pt content increased until about 66%. No further increase in the molar ratio resulted in any additional Pt incorporation into the alloy. As for the replacement of Cu with Pd, the thickening of the nanotubes was observed indicating that nanotubes composed of Pd nanoparticles were formed. Backscattered electron imaging and SEM-EDS revealed CuPd nanotubes with approximately 2.3% Cu content. These remarks indicate different evolution mechanism for the nanotubes in the two systems.