Insight into the selective catalytic reduction (SCR) of NO by NH3 over vana
dia/titania catalysts is obtained from a combination of Raman and FTIR spec
troscopic investigations and density functional theory (DFT) calculations.
Studies of the V-OH and V=O functional groups under different conditions co
upled with calculations of the stability and mobility of H atoms provide ev
idence that dynamic structural rearrangements may occur during the SCR reac
tion. Hydrogen atoms are bonded more strongly to oxygen atoms that are coor
dinated to a single vanadium atom (V=O species), compared to bonding at oxy
gen atoms that are coordinated to multiple vanadium atoms (e.g., V-O-V spec
ies); and, activation energy barriers for hydrogen transfer from a V=O spec
ies to another V=O species and to a V-O-V species are estimated from DFT ca
lculations to be 60 and 130 kJ/mol, respectively. This dynamic nature of hy
drogen transfer between oxygen atoms having different coordination environm
ents also appears to explain some of the spectroscopic changes observed for
vanadia/titania catalysts having different vanadia loadings.