Journal of The Electrochemical Society, 159 (4) F91-F96 (2012) F91 0013-4651/2012/159(4)/F91/6/$28.00 © The Electrochemical Society Electrochemical Oxidation of NH3 on Platinum Electrodeposited onto Graphite Electrode

The electrochemical activity for ammonia oxidation of Pt electrodes prepared by pulsed potentiostatic electrodeposition on graphite electrode was investigated by cyclic voltammetry, chronoamperometry and prolonged electrolysis with analysis of the reaction products. The morphology of Pt deposits was observed by scanning electron microscopy. It was demonstrated that the difference of morphologies of the Pt deposits has no impact on the activity of the electrode for the oxidation of ammonia. At around −0.2 V vs Hg/HgO, NH3 is oxidized to N2 whereas, at more positive potentials, the Pt electrode is poisoned by adsorbed N-species. The consequence of this poisoning is a dramatic drop of electrode performance for NH3 oxidation. In order to avoid this poisoning effect, periodic reducing potential pulses were applied to desorb poisoning species from the Pt surface and to recover the initial activity of the electrode for NH3 oxidation. Potentiostatic electrolyses revealed that electrode reactivation is highly efficient at potential more negative than −0.6 V and permits to significantly increase the NH3 conversion rate