Promotional effect of nitrogen-doping on a ceria unary oxide catalyst with rich oxygen vacancies for selective catalytic reduction of NO with NH3

Noble-metal catalysts have been limited in removal of NOx in diesel vehicles due to the poor NOx conversion in high air-fuel ratio, poor resistance to SO2 and earth rarity. Thus, earth-abundant and environmental-friendly CeO2 with outstanding oxygen storage (OSC) property attracts public attention. In this work, a novel nitrogen-doped (N-doped) unary ceria oxide catalyst with rich oxygen vacancies was developed by an ammonification strategy based on a flower-like CeO2. Benefitting from the N dopant and the resulted rich oxygen vacancies, the N-doped CeO2 exhibited a high NOx removal efficiency with a NOx conversion of > 95% and N-2 selectivity of > 95% over a wider temperature range (275-400 degrees C), and a higher gas hourly space velocity (GHSV) of 177,000 h(-1) than other ceria-based catalysts reported in the literatures. X-ray absorption spectroscopy and low-temperature electron spin resonance results revealed that nitrogen dopant contributed to the enrichment of surface oxygen vacancies, which were beneficial to SCR reaction. In situ DFRITS analysis demonstrated that nitrogen dopant resulted in the enrichment of Bronsted acid sites, inhibition of NH3 oxidation and formation of active nitrite species at high temperature, thus leading to the high NOx removal efficiency.