Oxidation of hydroxylamine on the rotating solid electrodes - I. Oxidation of hydroxylamine in protonated form

Hydroxylamine oxidation in acidic media at the rotating platinum, gold, and glassy carbon electrodes was investigated. It was found that the reaction occurred only at the platinum electrode. A single oxidation peak (instead of a wave) was observed at the rotating platinum electrode. Evidence for a kinetic hindrance of the reaction caused by the platinum oxide layer present at the electrode surface was shown. The reaction proceeds via NHOH, NOH, nitrous acid, and the final products are nitrate ions. The process involves hydroxylamine adsorption, which is the reason for the absence of the electrochemical signal in the case of gold and carbon, materials of lower catalytic activity. Hydroxylamine oxidation was accompanied by various homogeneous chemical reactions. The reaction of hydroxylamine with nitrous acid (intermediate product of hydroxylamine oxidation), yielding N2O, had a rate constant, estimated on the basis of the ring-disk experiments, equal to (6.4+/-0.4) 10(4) mol(-1) cm(3) s(-1). (C) 2004 The Electrochemical Society.