Electrocatalytic oxidation of ethanol on polypyrrole modified graphite electrode

Nickel-polypyrrole modified graphite electrodes (G/NiPPy) prepared by voltammetrice deposition were examined for their redox process and electrocatalytic activities towards the oxidation of ethanol in alkaline solutions. The methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) were employed. The cyclic voltammogram of G/NiPPy demonstrates the formation of α/ß crystallographic forms of the nickel oxyhydroxide under prolonged repetitive potential cycling in alkaline solution. In CV studies, in the presence of ethanol G/NiPPy modified electrode shows a significantly higher response for ethanol oxidation. The peak current of the oxidation of nickel hydroxide increase is followed by a decrease in the corresponding cathodic current in presence of ethanol. The anodic peak currents show linear dependency with the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of ethanol was found to be 2.4×10-6 cm2 s-1. A mechanism based on the electro-chemical generation of Ni3+ active sites and their subsequent consumptions by ethanol have been discussed and the corresponding rate law under the control of charge transfer has been developed and kinetic parameters have been derived. The charge transfer resistance accessible both theoretically and through the EIS have been used as criteria for deviation of rate constant.

Keywords:

conducting polymer , electrocatalytic , ethanol , modified electrode