The promoting mechanism of SO42− on CeO2 for selective catalytic reduction of NO by NH3: A DFT study

Ceria catalysts have attracted considerable interest in the NH 3 -SCR reaction. The modification of SO 4 2− into CeO 2 promotes the NH 3 -SCR reaction. NH 3 adsorption property and four possible reaction paths are further design over CeO 2 (111) and SO 4 2− –CeO 2 (111) surface. The results reveal that NH 3 adsorption of the Lewis acid site is stronger than the Brønsted acid site, and the adsorption energies of the Lewis acid site range from − 0.397 to − 0.963 eV with the modification of SO 4 2− . Thus, the introduction of SO 4 2− into CeO 2 increases the adsorption site stability of NH 3 . NH 3 adsorption is the first step in NH 3 -SCR reaction, and then, the key intermediates such as NH 2 , NH 2 NO, NNOH, NH 3 NO 2 species are found. Standard SCR reaction and fast SCR reaction constitute a catalytic cycle in CeO 2 catalyst. The different paths of NH 3 NO 2 and NH 2 NO formation are different, and it led to NNOH only emerge in the fast SCR reaction. Lewis acid site is main reaction site for the standard SCR reaction. Energy barriers of Lewis acid site range from 15.82 to 15.68 kcal/mol by the introduction of SO 4 2− , which makes the NH 3 -SCR reaction easily occur.