Measurements and modelling of the oxidation of ammonia over copper oxide (CuO) under conditions relevant to chemical-looping combustion with oxygen uncoupling show that CuO fully converts NH3 into NO or N-2 under most of these conditions. Our experiments demonstrate that considerable amounts of NO are formed when the oxygen carrier is fully oxidised. Decreasing the degree of oxidation of the oxygen carrier affected the selectivity of the NH3 oxidation towards NO. Ageing of the oxygen carrier had a similar effect. Modelling suggests that these results reflect a change in the rate of oxygen release from the CuO particles. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.