Facile preparation of mesoporous Cu–Sn solid solutions as active catalysts for CO oxidation

Abstract

With a facile co-precipitation method, a series of high surface area mesoporous Cu_xSn_1−xO_y solid solution catalysts have been synthesized and applied to CO oxidation. Compared with individual SnO₂ and CuO, the activity of these catalysts is remarkably improved. The highest activity is achieved on Cu_0.5Sn_0.5O_y, a catalyst with a Cu/Sn molar ratio of 0.5/0.5 and a Caramel-Treats-like morphology. It is revealed by XRD, SEM-EDX mapping and HR-TEM results that Cu²⁺ cations have been incorporated into the crystal lattice of rutile SnO₂ to form a uniform solid solution structure. As testified by N₂ adsorption–desorption and SEM results, these Cu_xSn_1−xO_y catalysts contain well-defined mesopores and possess high surface areas and improved pore volumes, which are favourable for the dispersion of the active sites, the diffusion of the reactants and the easy interaction between the reactants and the catalyst surface. Moreover, H₂-TPR and XPS results demonstrate that more active and loosely bounded oxygen species have been formed on the surface of these catalysts. It is believed that these are the predominant reasons leading to the superior CO oxidation activity over the Cu_xSn_1−xO_y catalysts. Notably, these Cu_xSn_1−xO_y catalysts are also resistant to water vapour deactivation, indicating they have the potential to be used in real exhaust control processes.