A Cu electrode can reduce hydroxylamine (HA) in KCl solution but losses its activity very quickly. However, while Cu particles are immobilized on a Pt surface, the resultant electrode showed excellent catalytic activities towards HA reduction reactions compared to those shown by a Cu or Pt electrode. On the Pt-Cu surface, HA molecules involved two electron transfer reduction reaction yielding ammonia as an end product. The HA reduction process follows a first order kinetics on the Pt-Cu surface. In this study, heterogeneous electron transfer kinetics was studied to unveil the reduction pathway. It was observed that the reduction process occurs by a concerted mechanism having an intrinsic barrier of 0.24 eV. The formal potential of the reduction process was found to be -0.49 V with respect to Ag/AgCl (sat. KCl) reference electrode. The developed Pt-Cu electrode may be used as a HA sensor which exhibited a linear range from 5 to 110 mM HA with a limit of detection of 0.628 mM and good selectivity towards HA in water with recovery from 99 to 110%. (C) 2019 Elsevier Ltd. All rights reserved.