Effect of the halogen ions on the cyclic voltammetry behaviour of the nitrate ion reduction in sulphuric acid solutions

The electrochemical reduction of the nitrate ion on copper electrode in 0.1 M H 2 SO 4 in the presence of I-, Br, Cl - ions was studied by cyclic voltammetry. Low concentration of iodide (10 - 7 M), bromide (10 - 6 M) and chloride (10 - 5 M) were sufficient to cause the shift of the peak potential of the nitrate reduction to more negative values and to reduce the peak current. The increase of the concentrations (10 - 5 M for I- and 2.5 x 10 - 5 M for Br) was made so that nitrate reduction be masked by hydrogen evolution. Increase of chloride concentration to 10 - 3 M determined the increase of the peak current compared with solutions without Cl- ions. The results are explained on the basis of the competitive adsorption of the halide ions and reactant species in the electrical double layer.