Search

• Copper dispersion on a rod-shaped ceria was examined with respect to copper loading. • Monolayer and bilayer copper clusters were dominate at copper loading of less than 15 mol.%. • Multi-layered copper clusters and faceted nanoparticles were formed at higher copper loadings. • The active copper-ceria interface was constructed by the positively-charged copper atoms with the oxygen vacancies on ceria. • The WGS activity increased linearly with copper loading up to 15 mol.%. Cu species in the forms of layers, clusters and particles were dispersed on a rod-shaped ceria by a deposition-precipitation method and the resulting Cu/CeO 2 catalysts were tested for the low-temperature water-gas shift reaction. The structural, chemical and surface properties of the Cu/CeO 2 catalysts were analyzed by spectroscopic and microscopic techniques. It was identified that dispersion of copper on the rod-shaped ceria strongly depended on the metal loading (1–28 mol%): lower contents resulted in copper monolayers and/or bilayers while higher loadings led to multi-layered clusters and faceted particles. The copper-ceria interface was constructed by an intimate bonding of positively-charged copper atoms with oxygen vacancies on ceria, in a form of Cu+-O v -Ce3+, involving the electronic and geometric interactions between the copper atoms in the metal species and the oxygen vacancies on ceria. The overall activity increased linearly with the copper content in the range of 1–15 mol%, contributed mainly by copper monolayers and/or bilayers. Further increasing Cu loading up to 28 mol% only slightly enhanced the activity because of the presence of multilayered and crystalline Cu particles. This finding demonstrates that the dispersion of copper on the rod-shaped ceria depends on the loading of copper in the Cu/CeO 2 catalysts, which is associated with the number and density of the active sites. [ABSTRACT FROM AUTHOR]