Palladium/Copper-Graphene Nanohybrid as an Effective Electro-Catalyst for Hydrazine Oxidation

In this research, copper-reduced graphene oxide (Cu-rGO), graphene-palladium (Pd-rGO) and palladium/copper-graphene (Pd/Cu-rGO) nanohybrids were prepared and used as electrode materials towards electrocatalysis of hydrazine oxidation. For this purpose, firstly, GO was prepared by modified Hummer's method. In the following, for preparation of the Cu-rGO nanohybrid, GO and metallic precursor were reduced by hydrazine monohydrate, simultaneously. Then, Pd/Cu-rGO nanohybrid was obtained by chemical reaction between Cu-rGO nanohybrid and acidic palladium chloride solution via galvanic replacement of Cu nanoparticles with PdII. Morphology and nanoparticles size were investigated by field emission-scanning electron microscopy (FE-SEM). FE-SEM studies showed the formation of Cu and Pd/Cu nanoparticles with average size about 20 and 15 nm on the graphene surface, respectively. Elemental mapping of the prepared nanohybrids demonstrated uniform dispersion of Cu and Pd/Cu nanoparticles on the graphene substrate. Functional groups at GO and graphene were determined by Fourier transform infrared spectroscopy. By X-ray diffraction analysis, structure of the nanoparticles in nanohybrids was identified. The results of electrochemical impedance spectroscopy showed that the modification of glassy carbon electrode (GCE) with the synthesized nanohybrids effectively reduced the charge transfer resistance between the modified electrode and redox species. The capability of the modified GCE for electrocatalysis of hydrazine oxidation was studied in 0.1 M PBS solution (pH=7.0). The obtained results showed the acceptable electro-catalytic activity of modified electrode towards hydrazine oxidation. Also, Pd/Cu-rGO nanohybrid in addition of the high surface area, due to the synergistic effect between Cu and Pd showed higher electro-catalytic activity towards hydrazine oxidation.