SYNTHESIS AND CHARACTERIZATION OF Ni-Cu/RGO NANOCOMPOSITE FOR METHANOL ELECTRO -OXIDATION

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.