Reduced graphene oxide supported CuO-CeO2 nanospheres (CuO-CeO2/rGO) were prepared by a facile hydrothermal method. The chemically bonded CuO-CeO2/rGO composites effectively enhanced their activity in the CO preferential oxidation (CO-PROX), while moderate rGO content (7mg) exhibited an improvement on the catalytic activity. The prepared composite with 14 wt% rGO showed the highest catalytic activity, exceeding that of pure CuO-CeO2 and mechanically mixed CuO-CeO2 and rGO, respectively. The enhancement in the CO-PROX activity was attributed to the synergetic effect between rGO and CuO-CeO2 nanospheres. Besides supported rGO layers as excellent electron transporters, CuO-CeO2 nanospheres in turn act as the skeleton to brace two-dimensional structure to prevent from further curling, crumpling and aggregation of rGO. In the presence of capping agents during synthesis, limited catalytic activities of CuO-CeO2/rGO was observed due to the restrained interfacial charge transfer between CuO-CeO2 and rGO layers. This work, focusing on effective CO-PROX through a chemically bonded interface between CuO-CeO2 and rGO, can provide a new insight for design of new heterogeneous catalysts.Graphical AbstractChemical bonded CuO-CeO2/rGO nanocomposites synthesized by a facile hydrothermal approach have shown high CO-PROX activity. Excellent charge transport between rGO layers and CuO-CeO2 nanospheres via their interfaces leads to enhanced catalytic activity for CO-PROX. [GRAPHICS] .