Electrocatalytic oxidation of ammonia in the neutral medium using Cu2O.CuO film immobilized on glassy carbon surface

Abstract

Enhanced catalytic response towards ammonia oxidation was observed at Cu 2 O.CuO-GCE electrode. Ammonia undergoes 3 electron transfer reaction to produce N 2 as the end product. The first electron transfer was evaluated to be the rate determining step, therefore, the reaction intermediates (NH 2 ads , NH ads , N ads ) doesn’t control the rate of reaction. • Sustaining the stability of the electrode is the main challenge in electrochemical oxidation of NH 3. • We discuss the role of mixed Copper oxides (CuO-Cu 2 O) on Glassy Carbon electrode for NH 3 oxidation. • The modified electrode shows good catalytic stability with increasing NH 3 concentration. • Neutral medium is found to be most favorable for NH 3 oxidation at CuO-Cu 2 O-GCE electrode. Electrocatalytic ammonia oxidation reaction (AOR) was executed on the copper oxide layer, electrochemically deposited on a glassy carbon electrode (GCE) surface. The XPS analysis revealed that the oxide film contains 80% Cu(I) and 20% Cu(II) species. The EIS analysis suggests that the resultant surface can catalyze ammonia oxidation reactions efficiently. The as prepared GCE-Cu 2 O.CuO favored the neutral medium for executing AOR with a degradation rate of 3.76 × 10 −4 mol min −1 cm −2 . Kinetic investigation shows that ammonia oxidation involves a three electron transfer first-order reaction. Tafel analysis of current–potential polarization curves indicates that species such as NH 3 or NH ads and NH 2ads intermediates do not influence the reaction rate, which made the electrode unique for carrying out AOR. The formal potential value of AOR was evaluated to be ~0.7 V vs Ag/AgCl (sat.KCl) having standard rate constant ( k° ) of 5.52 × 10 −6 cm/s.