Morphology and nanosize effects of ceria from different precursors on the activity for NO reduction

The present work comparatively explored the morphology and size-dependent reduction and activity of CeO2 nanostructures for NO reduction. CeO2 nanorods were prepared by Ce(NO3)3, while spherical-like nanoparticles with an average size of 4–6 nm were obtained from (NH4)2Ce(NO3)6 and Ce(SO4)2. As compared with CeO2 nanorods, these nanoparticles (4–6 nm) showed the larger lattice strain and higher activity for NO reduction, which was due to the nanosize effect that significantly improved the intrinsic reducibility of surface oxygen and facilitated the formation of oxygen vacancies. In addition, the adsorption type and configuration of NO was similar over these different shaped ceria. However, CeO2 nanoparticles from tetravalent cerium showed the greater capacity to activate the adsorbed NO species than nanorods from the tervalent nitrates.

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► Compared with CeO2 nanorods prepared from Ce(NO3)3, CeO2 nanoparticles from (NH4)2Ce(NO3)6 show the smaller size (4–6 nm) and higher lattice strain.
► CeO2 nanoparticles from (NH4)2Ce(NO3)6 exhibit the higher activity for NO reduction than nano-CeO2 from Ce(SO4)2, CeO2 and Ce(NO3)3. This is probably due to its nanosize effect that improves its reducibility of surface oxygen and facilitates the formation of surface oxygen vacancy.
► The adsorption type and configuration of NO species is similar over these different shaped ceria. However, CeO2 nanoparticles from tetravalent cerium show the greater capacity to activate the adsorbed NO species than nanorods from the tervalent nitrates.