Cu-Ce-La-Ox as efficient CO oxidation catalysts: Effect of Cu content
Date
2020Author
AlKetbi, MaithaPolychronopoulou, Kyriaki
Abi Jaoude, Maguy
Vasiliades, Michalis A.
Sebastian, Victor
Hinder, Steven J.
Baker, Mark A.
Zedan, Abdallah F.
Efstathiou, Angelos M.
ISSN
0169-4332Source
Applied Surface ScienceVolume
505Google Scholar check
Metadata
Show full item recordAbstract
Nanograins of Ce-La-xCu-O mixed metal oxides (wherex = 3, 5, 7, 10, 20 at.%), of approximately 16 nm2 area size, and having all the metal cations homogeneously distributed, are tested as ternary catalytic materials towards the CO oxidation in the 100–475 °C range. Preservation of the cubic ceria lattice structure in those catalysts following La3+ (heavy) and Cu2+ (light) metal cations doping is confirmed based on the powder X-ray diffraction and Raman shift studies. From X-ray photoelectron spectroscopy studies, the presence of mixed Ce3+/Ce4+ and Cu2+/Cu1+ oxidation states was confirmed, which was more profound in the low Cu-content Ce-La-xCu-O catalysts. The copper doping is also found to increase the concentration of oxygen vacant sites in the doped-CeO2 solid as demonstrated from the increase of the Raman intensity ratio IOv/IF2g of 1.58 and 1.78 with the increase in copper content from 7 to 20 at.% as compared to the lower value of 0.44 obtained for the Cu-free catalyst (Ce-La). The mobility of the surface and bulk oxygen ions in the lattice of such doped-CeO2 materials is further investigated using 16O/18O transient isothermal isotopic exchange (TIIE) experiments, and is found to be Cu at.% dependent. For the case of Ce-La-20Cu, the participation of the lattice oxygen (OL) in the reaction mechanism has been demonstrated using transient experiments. Accordingly, the specific rate (μmol CO m−2s−1) of the CO oxidation reaction is found to be higher for the Ce-La-20Cu and Ce-La-7Cu catalysts, corroborating thus the presence of more mobile/labile oxygen species in those ternary catalysts as opposed to the other lower copper compositions.