Reaction Pathways of the Selective Catalytic Reduction of NO with NH on the α-FeO(012) Surface: a Combined Experimental and DFT Study.

FeO-based catalysts have promising potential in the selective catalytic reduction (SCR) of NO with NH with the advantages of environmental friendliness, excellent medium-high SCR activity, good N selectivity, and high SO tolerance. However, the NH-SCR mechanism over FeO-based catalysts remains highly uncertain and controversial due to the complex nature of the SCR reaction. Herein, the NH-SCR reaction pathways over the α-FeO(012) surface are elucidated at the atomic level by density functional theory calculations and experimental measurements. We demonstrate that, different from the NH activation mechanism in numerous SCR catalytic systems, the reaction tends to follow the NO activation mechanism, in which NO activated at Fe sites reacts with NH to form a NHNO intermediate and further decomposes into N and HO, in synchronization with the formation of a surface OH group. Subsequently, the catalyst is regenerated by an O-assisted surface-dehydrogenation process. The activation of NO as well as the formation of the NHNO intermediate is the rate-determining step of the complete SCR cycle. This study enhances the atomic-level understanding toward the NH-SCR reaction and provides insights for the development of FeO-based SCR catalysts.