Polypyrrole Modified Copper Electrode for Nitrate and Nitrite Reduction in Neutral Solutions

Abstract

Conducting polypyrrole (Ppy) film was synthesized electrochemically onto a copper electrode in oxalate, oxalic acid and salicylic acid solutions. The electrochemical oxidation of pyrrole to form polypyrrole film and the electroreduction of nitrate and nitrite ions at synthesized PPy modified copper electrodes (Ppy/Cu) in potassium chloride aqueous solutions were studied by cyclic voltammetry. Polypyrrole film formation and the activity of the modified Ppy/Cu electrode for nitrate and nitrite reduction were found to be dependent on synthesis medium and conditions: pH, content and concentrations of the electrolytes; pyrrole concentration; electrode potential; electrolysis duration. The finishing and storage conditions of the prepared Ppy/Cu modified electrodes, such as drying duration and temperature; soaking duration in water before use, also affect their catalytic activity for nitrate and nitrite reduction. The highest reduction currents of nitrate and nitrite were obtained for the nanoporous structured Ppy film prepared in salicylic acid solution. Nitrate and nitrite reduction occurred at cathodic potentials of ca. -0.70 V and -0.85 V (Ag/AgCl) respectively, and the peak potentials ranged from -1.00 V to -1.15 V (Ag/AgCl). In the potassium chloride aqueous solution the reduction of nitrate and nitrite ions on the Ppy/Cu electrode was found irreversible.