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Issue 11, 1995
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NO reaction at surface oxygen vacancies generated in cerium oxide


NO adsorption on CeO2 pre-outgassed at different temperatures (Tv) has been studied by EPR and FTIR. The results are compared with those obtained by measuring the products of the reaction, performed at 323 K, between NO and CeO2 samples activated by previous heating under N2 flow. EPR results indicate that, for Tv[gt-or-equal] 573 K, NO molecules are adsorbed in radical form at 77 K and react at 298 K with surface oxygen vacancies generating diamagnetic products. FTIR spectra show correspondingly the formation of hyponitrites, nitrites and nitrates upon NO adsorption at 298 K on CeO2 outgassed at different temperatures. The hyponitrites can decompose at ambient temperatures to produce N2O; the process leads to modification (probably reoxidation) of the surface centres initially present. This can be followed by O2 adsorption and EPR spectroscopy, which shows that O2 adsorbed on the modified vacancies is less stable than on CeO2 without NO adsorbed, its reaction leading in some cases to the formation of peroxynitrate-type radicals. The reaction at 323 K of NO on the pretreated CeO2 surface produced N2O for pretreatment temperatures TF[gt-or-equal] 573 K, in amounts increasing with TF. The results indicate that surface centres containing associated oxygen vacancies are active sites for this process.

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Article information

J. Chem. Soc., Faraday Trans., 1995,91, 1679-1687
Article type

NO reaction at surface oxygen vacancies generated in cerium oxide

A. Martínez-Arias, J. Soria, J. C. Conesa, X. L. Seoane, A. Arcoya and R. Cataluña, J. Chem. Soc., Faraday Trans., 1995, 91, 1679
DOI: 10.1039/FT9959101679

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