Electrochemical oxidation of ammonia in alkaline solutions: its application to an amperometric sensor

The electrochemical oxidation of ammonia was studied at room temperature on a black platinum electrode, iridium black, a mixture of both and Pt-Ir electrodeposits in alkaline solutions of potassium hydroxide. The current density for the ammonia discharge was proportional to the ammonia concentration in the range from 50 to 200 ppm of the functioning of the sensor. It was found that the current density on the platinum-iridium mixture is higher than on platinum black and iridium black. On the other hand, Pt-Ir electrodeposits on Au and Pt were prepared and characterized by X-ray analysis. The diffractograms evidenced the presence of a continual platinum-iridium solid solution where platinum is replaced by iridium atoms in the fee structure. The Pt-Ir electrodeposits showed a good response to the ammonia gas. (C) 1997 Elsevier Science Ltd.