Vertically standing Cu^sub 2^O nanosheets promoted flower-like PtPd nanostructures supported on reduced graphene oxide for methanol electro-oxidation

The present study reports a simple electrochemical approach to the fabrication of a new nanocomposite containing PtPd nanoflowers (NFs) promoted with two-dimensional (2D) nanosheets (NSs) structure cuprous oxide (Cu2O) supported on reduced graphene oxide (rGO) (PtPd-NFs/Cu2O-NSs/rGO). Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Raman spectroscopy, and energy dispersive X-ray spectroscopy are used for characterization of the PtPd-NPs/Cu2O-NPs/rGO. SEM images showed that vertical-standing arrays of Cu2O with an edge length up to 1 μm and thickness of about 20 nm are electrodeposited on the surface of rGO film. Also, PtPd needle-like NFs with visible and clear pricks totally covered the Cu2O-NSs/rGO surface. Also for comparison, Cu2O nanoparticles (NPs) and PtPd-NPs were prepared by the electrodeposition method at the surface of rGO/GCE (PtPd-NPs/Cu2O-NPs/rGO). Taking methanol oxidation as a catalytic reaction model in acidic medium, the catalytic activities of the prepared catalysts are studied through cyclic voltammetry, chronoamperometry, chronopotentiometry and electrochemical impedance spectroscopy. Interestingly, the proposed catalyst PtPd-NFs/Cu2O-NSs/rGO exhibited an outstanding electrocatalytic activity, lower onset potential and high level of poisoning tolerance toward methanol oxidation in acidic media. The obtained results can be ascribed to the synergetic effect between bimetallic PtPd, Cu2O, and rGO. Also, Cu2O nanostructure can be appeared as a catalytic mediator, facilitating the charge transfer and enhance the CO poisoning oxidation through spillover of OH to PtPd surface. Certainly, the unique shape and morphology of the Cu2O-NSs and PtPd-NFs have a significant influence on the catalytic behavior of the nanocomposite. So, according to results, PtPd-NFs/Cu2O-NSs/rGO can be considered as a promising anode catalyst in direct methanol fuel cells.