ELECTROCHEMICAL STUDY OF NO CONVERSION FROM FE(II)-EDTA-NO COMPLEX ONPT ELECTRODES

The Fe(LI)-ethylenediaminetetraacetic acid (EDTA)-NO complex formed by interaction of gaseous nitrous oxide (ca. 200 ppm) and Fe(II)-EDTA in aqueous solution was found to be converted electrochemically on plati num electrodes at potentials below ca. -0.6 V-SCE indicating the catho dic reduction of NO. In addition to our previous studies by which the indirect conversion of NO with dithionite as a redox mediator was conf irmed, the present results should elucidate the possibility of the dir ect electrochemical conversion of NO in mediator-free solutions. To cl early separate this process from other reactions in the system, the el ectrochemical behavior of Fe(II)-EDTA and Fe(III)-EDTA was studied ove r a wide potential range at different pH values. Five electrode reacti ons could be identified, which include the oxidation/reduction of Fe2/Fe3+ in the EDTA complex, the reduction of EDTA, the-reduction of pro tons, the cathodic deposition of iron, and the anodic decomposition of EDTA. The electrochemical deposition of iron from Fe(II)-EDTA at pote ntials E < -1.0 V-SCE was confirmed by electrochemical quartz crystal microbalance measurements and energy-dispersive x-ray analysis.