Chemical looping combustion (CLC) is an emerging, new technology for carbon capture and storage (CCS). Copper-based oxygen carriers are of particular interest due to their high oxygen carrying capacity and reactivity, low tendency for carbon deposition, and exothermic reduction reactions. In this work, CuO-based and Al(2)O(3)-stabilized oxygen carriers with high CuO loadings were developed using a coprecipitation technique. The cyclic redox performance of the synthesized oxygen carriers was evaluated at 800 °C in a laboratory-scale fluidized bed reactor using a reducing atmosphere comprising 10 vol. % CH(4) and 90 vol. % N(2). The CuO content in the oxygen carrier was found to increase with the pH value at which the coprecipitation was performed. The oxygen carrying capacity of the oxygen carrier containing 87.8 wt % CuO was found to be high (5.5 mmol O(2)/g oxygen carrier) and stable over 25 redox cycles. Increasing the CuO content further, i.e. > 90 wt %, resulted in materials which showed a decreasing oxygen carrying capacity with cycle number. It was also shown that the incorporation of K(+) ions in the oxygen carrier can avoid the formation of the spinel CuAl(2)O(4) and significantly reduce carbon deposition.