Nickel oxide carbon nanofiber composite for electrochemical oxidation of methanol

Abstract

Electrospun fibers of a mixture of polyvinylpyrrolidone (PVP), polyaniline (PANI) and graphene were stabilized for 2 h at 200 °C and then carbonized at 800 °C for 5 h. Composites were prepared by depositing Ni(OH)2 on the carbon nanofibers (CNFs) and calcining them at different temperatures. The composites were characterized using XRD, TEM and SEM. The effect of the calcination temperatures on the electrochemical catalytic properties towards methanol (MeOH) oxidation was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The analysis of the chronoamperometry measurements confirmed a significant increase in the real surface area for the CNF/NiO composite as the calcination temperature increases. The real surface area is increased at calcination temperatures of 400 and 500 oC more than 20 times higher than that calcined at 300 oC. The oxidation of MeOH was not found to be a purely diffusion controlled process. The CNF/NiO composite has shown, not only, a good stability as the potential was cycled between a large potential window, but also, the electrocatalytic properties was enhanced which was attributed to the surface activation during the cyclic process. The impedance parameters were calculated from the EIS measurements proved that this system has two time constants: one for the adsorption and the other for the charge transfer.