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

Abstract

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, N₂ 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 H₂ at relatively low temperature.