Uncovering the Dinuclear Mechanism of NO 2 -Involved NH 3 -SCR over Supported V 2 O 5 /TiO 2 Catalysts.

Commercial vanadium oxide catalysts exhibit high efficiency for the selective catalytic reduction (SCR) of NO with NH 3 , especially in the presence of NO 2 (i.e., occurrence of fast NH 3 -SCR). The high-activity sites and their working principle for the fast NH 3 -SCR reaction, however, remain elusive. Here, by combining in situ spectroscopy, isotopic labeling experiments, and density functional theory (DFT) calculations, we demonstrate that polymeric vanadyl species act as the main active sites in the fast SCR reaction because the coupling effect of the polymeric structure alters the elementary reaction step and effectively avoids the high energy barrier of the rate-determining step over monomeric vanadyl species. This study unveils the high-activity dinuclear mechanism of the NO 2 -involved SCR reaction over vanadia-based catalysts and provides a fundamental basis for developing high-efficiency and low V 2 O 5 -loading SCR catalysts.