Abstract:
Ni-Cu/reduced graphene oxide (RGO) nanocomposite was prepared by using chemical
reduction method for methanol electro-oxidation. Ni-RGO and Cu-RGO were also synthesized
using the same method to compare their performance for methanol electro-oxidation. The
synthesized nanocomposites Ni-RGO, Cu-RGO and Ni-Cu/RGO were characterized using xray
diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared
spectroscopy (FTIR), Energy dispersive X-ray spectroscopy (EDX) and ultraviolet-visible
spectroscopy (Uv-vis). Electrochemical properties of the nanocomposites were studied by
employing cyclic voltammetry (CV), chronoamperometry and electrochemical impedance
spectroscopy (EIS). Ni-Cu/RGO exhibited a superior electrocatalyst towards methanol
oxidation in alkaline medium as evidenced from its high current density (440 mA) compared to
that of Ni-RGO (353 mA) and Cu-RGO (242 mA). This is probably because of Ni-Cu/RGO
nanocomposites high electrocatalytic surface area (89.1cm2
/g) and the synergetic catalytic
effect coming from both Ni and RGO. Besides, Ni-Cu/ RGO may be tolerance to the poisoning
effect from intermediates accumulated on the surface of the electrode during the redox
reaction. The effect of scan rate on methanol oxidation on surface of Ni-Cu/RGO was also
investigated using CV. It was noticed that the peak current increased with scan rate while
peak potential slightly shifted toward a more positive value. Moreover, plot of peak current
versus square root provided a straight line indicating the reversibility of the process. The diffusion coefficient of methanol was found to be 2.6x10-4
cm
2
/s. Furthermore, the Ni-Cu/ RGO
study using EIS demonstrated fast electron transfer kinetics in comparison to those of the
binary systems. Therefore, Ni-Cu/RGO nanocomposite is a new electrode material and it can
be utilized for the electrochemical oxidation of methanol in fuel cells.
