摘要：To understand the dispersion behavior of metal oxides on composite oxide supports and with the expectation of developing more feasible catalysts for soot oxidation,CuO/La_(2)Sn_(2)O_(7)samples containing varied CuO loadings were fabricated and characterized by different techniques and density functional theory *** these catalysts,a spontaneous dispersion of CuO on the La_(2)Sn_(2)O_(7)pyrochlore support formed,having a monolayer dispersion capacity of 1.90 mmol CuO/100 m^(2) La_(2)Sn_(2)O_(7)*** loaded below this capacity,CuO exists in a sub-monolayer or monolayer state.X-ray photoelectron spectroscopy(XPS),Raman spectroscopy,and Bader charge and density of states analyses indicate that there are strong interactions between the sub-monolayer/monolayer CuO and the La_(2)Sn_(2)O_(7)support,mainly through the donation of electrons from Cu to Sn at the B-sites of the *** contrast,Cu has negligible interactions with La at the *** suggests that,in composite oxide supports containing multiple metals,the supported metal oxide interacts preferentially with one kind of metal cation in the *** Raman,in situ diffuse reflectance infrared Fourier transform spectroscopy,and XPS results confirmed the formation of both O2^(-)and O2^(2-)as the active sites on the surfaces of the CuO/La_(2)Sn_(2)O_(7)catalysts,and the concentration of these active species determines the soot combustion *** number of active oxygen anions increased with increase in CuO loading until the monolayer dispersion capacity was *** the monolayer dispersion capacity,microsized CuO crystallites formed,and these had a negative effect on the generation of active surface oxygen *** summary,a highly active catalyst can be prepared by covering the surface of the La_(2)Sn_(2)O_(7)support with a CuO monolayer.

摘要：With the objective to investigate the structure-reactivity relationship of CuO/SnO2 and eventually design more applicable catalysts for soot combustion,catalysts with different CuO loadings have been prepared by impregnation *** using X-ray diffraction and X-ray photoelectron spectroscopy extrapolation methods,it is disclosed that CuO disperses finely on the SnO2 support to form a monolayer with a capacity of 2.09 mmol 100 m^-2,which equals 4.8 wt%CuO *** the CuO loading is below the capacity,it is in a sub-monolayer ***,when the loading is above the capacity,CuO micro-crystallites will be formed that coexist with the CuO *** soot combustion activity of the catalyst increases with the CuO loading until it reaches the monolayer dispersion capacity.A further increase in the CuO loading has no evident influence on the *** results have testified that with the addition of CuO onto the SnO2 support,a surface-active oxygen species can be formed,the amount of which also increases significantly with the increase in the CuO loading until it reaches the monolayer dispersion *** the CuO loading further has no evident impact on the amount of surface ***,an apparent monolayer dispersion threshold effect is observed for soot combustion over CuO/SnO2 *** is concluded that the amount of surface-active oxygen sites is the major factor determining the activity of the catalyst.