Chemisorption and Photoadsorption of NO on Cerium(IV) Oxide

CeO 2 showed high adsorptivity (4.9 molecules/nm 2 ) for NO at 303 K. The adsorbed species of NO on CeO 2 in the dark were the NO dimer and/or dinitrosyl, nitrosyl, and NO 2 - . About 40% of the NO adsorbed in the dark was chemisorbed mainly as NO 2 - . N 2 O seemed to be liberated into a gas phase via the intermediate species, such as the NO dimer. The UV irradiation to CeO 2 −NO systems at 303 K induced the photoadsorption of NO and the photocatalytic formation of N 2 O. Most of the photoadsorbed species were chemisorbed, mainly as photooxidized species, NO 2 - and NO 3 -; all other photoadsorbed species were reversibly adsorbed as nitrosyl and dinitrosyl. A frequency shift was observed in a few IR bands of the adsorbed NO, which might have arisen from the photoreduction of Ce 4+ to Ce 3+ .