Structure–activity relationship of VOx/CeO2 nanorod for NO removal with ammonia

• Vanadia species suppress the reducibility and defect sites of ceria.
• Polymeric VOx, ceria provide Lewis and CeVO4 provide Brønsted acid sites.
• Polymeric VOx low energy barriers and CeVO4 increase rate constant.
• The reaction mechanism depends on the temperature.

A series of vanadia supported on ceria nanorods are prepared by impregnation method for selective catalytic reduction (SCR) of NO with ammonia. Two kinds of vanadia species (VOx) (oligomeric and polymeric VOx) and CeVO4 are dispersed on the ceria surface according to the vanadium surface density. These species slightly suppress the catalyst reducibility and concentration of surface oxygen defects rather than distort the ceria cubic lattice or enlarge the BET surface areas. Polymeric VOx and CeO2 create the Lewis acid sites and CeVO4 could be served as the Brønsted acid sites. Polymeric VOx provide new active sites compared with pure CeO2 for the SCR reaction and CeVO4 enhance the number of active sites. Moreover, part of the Lewis acid sites might be converted into the Brønsted acid sites at high temperature under the SCR gas flow. According to the investigations of the reaction mechanism, both Lewis and Brønsted acid sites are reactive with gaseous NO. At low temperature, cis-N2O22− and dimer (NO)2 are active, while surface nitrite or nitrate species are active at high temperature.

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