Catalytic activity for CO oxidation of Cu-CeO2 composite nanoparticles synthesized by a hydrothermal method

A facile hydrothermal method has been developed for the synthesis of nanosized Cu-CeO2 composites with various Cu contents. The obtained catalysts, with a Cu/CeO2 atomic ratio in the range of 0-40%, were characterized as to their structure, morphology, and redox features by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N-2 physisorption, and temperature programmed reduction with hydrogen. The experimental results show that the particles are highly crystalline CeO2 nanopowders of 5-8 nm primary particle size and the Cu nanoparticles indeed coexist with the CeO2 nanoparticles (cubic fluorite CeO2). The influence of Cu contents on their catalytic performance for CO oxidation was also studied. As for the catalytic reactivity, nanosized Cu-CeO2 composites have a higher catalytic activity than CeO2 in CO oxidation. It is ascribed to the effect between the cycle transition of Ce4+/Ce3+, oxygen vacancies and surface area, which are induced by copper. The catalytic activity of the Cu-CeO2 composites exhibits Cu content dependence where the best catalytic activity occurs at a Cu/CeO2 atomic ratio of 30%. In addition, nanosized Cu-CeO2 composites also show high catalytic activity for selective oxidation of CO in excess H-2 at relatively low temperature.