The inhibition mechanism of NO generation in NH-SCR process by water vapor.

N₂O is a typical by-product in the NH-SCR process, which requires urgent resolution due to its negative economic and environmental impacts. This study investigates in detail the mechanism of NO generation on the surface of the Mn-Ce/TiO catalyst (Mn-Ce/TiO-ZS) with anatase {001} facets preferentially exposed. The deep oxidation of NH and *NH capture of NO via O were proved to be the dominant NO generation pathways. The production of NO was remarkably reduced by the introduction of a low percentage of water vapor (HO). The results revealed that low percentage of HO was capable of enhancing the acid sites on the catalyst surface and facilitating the generation of active hydroxyl species. These active species inhibited the deep dehydrogenation of ammonia and the disintegration of nitrate species on the catalyst surface, as well as suppressing the generation of NO.