Cyclic Voltammetric Studies of Nitrate and Nitrite Ion Reduction at the Surface of Iridium‐Modified Carbon Fiber Electrode

Abstract

The electroreduction of nitrate and nitrite on iridium‐deposited carbon fiber electrode in aqueous sodium perchlorate solutions of pH 7 was studied using cyclic voltammetric techniques. Results obtained on the modified electrode support a two‐step nitrate reduction mechanism in which nitrate is first reduced to nitrite at during the negative scan and further reduced to ammonia at during the anodic scan. An oxidation peak for the unreduced nitrite was observed at −300 mV (Ag/AgCl). A Tafel slope of approximately 178 mV/dec and a pseudo‐first‐order rate constant of were determined for the cathodic reduction peak while Tafel slope of 18.9 mV/dec and were obtained for the anodic reduction peak. The Tafel slopes obtained also support the two‐step mechanism. The results obtained strongly suggest a minimal effect of pH on nitrate reduction in the pH range of 2.0–13.0 in solution at the surface of iridium‐coated carbon fiber electrode. © 2000 The Electrochemical Society. All rights reserved.