Flame spray pyrolysis synthesized CuO-TiO2 nanoparticles for catalytic combustion of lean CO

Abstract

In this work, CuO-TiO2 nanoparticles with different CuO mass contents of 2%, 8%, 12%, and 20% are synthesized by flame spray pyrolysis (FSP) method and applied to catalytic combustion of lean CO. The nano-catalyst is characterized by N2-physisorption isotherms, X-ray diffraction (XRD), transmission electron microscopy (TEM), H2-TPR (temperature-programmed reduction) and X-ray photoelectron spectroscopy (XPS). All the catalysts possess a high specific surface area, of which the CuO-TiO2 nanoparticles with 2 wt.% Cu (2CT) is as high as 98 m2/g, and exhibits a spherical structure with a diameter of 15–20 nm. Compared with other methods, the FSP method can significantly improve the loading of CuO without producing large crystalline CuO particles on the catalyst surface. Interestingly, the addition of CuO will essentially change the lattice structure of TiO2 for all catalysts, including its crystal spacing and XRD diffraction angle. Copper cations are embedded in TiO2 lattice to promote the transformation from anatase to rutile by producing oxygen defect at high flame temperature. The interaction between CuO and TiO2 has significant influence on its physicochemical properties. A lower onset reduction temperature on the sample with higher CuO loading is obtained due to the hydrogen spillover effect in H2-TPR test. Moreover, the loaded CuO increases the content of more stable rutile phase in the materials, so that it reduces the strong metal-support interaction (SMSI) effect of CuO and anatase phase to improve the properties of CO catalytic combustion. The synthesized CuO-TiO2 nanoparticles can achieve complete combustion conversion of lean CO at lower temperature of 120°C.