Revealing the critical properties of titania supports required for enhancing the SCR activity of supported vanadia catalysts

The catalytic performance of TiO 2 -supported VO x catalysts (VO x /TiO 2 ) in selective catalytic reduction (SCR) reactions depends sensitively on the interactions between the support and surface metal oxides . These VO x -TiO 2 interactions have been studied for decades, and yet the effect of support properties on VO x species and their catalytic activity remains controversial. This study explores the correlation between the NO conversion activity and the specific surface area , crystalline phase (anatase or rutile), and surface hydroxyl group content of TiO 2 supports that disperse VO x species. Thermal treatments at 600–800 °C induce phase transformations of TiO 2 from anatase to rutile, leading to defective TiO 2 surfaces that promote H 2 O dissociation by lowering dissociation free energies . These transformations increase the prevalence of hydroxyl groups on the rutile TiO 2 surface, compensating for losses in the dehydration reactions during thermal treatments. These effects, along with decreased specific surface areas of thermally treated TiO 2 , lead to hydroxyl group surface densities that favour the formation of active oligomeric VO x species, which exhibit higher activity than their monomeric counterparts or aggregated V 2 O 5 crystallites . This phase-transformed rutile also shows certain activity advantages as supports compared to the initial anatase. These conclusions are derived from combined synthetic, kinetic, spectroscopic, and theoretical (density function theory calculations) approaches. They provide insights into the relationship between NO conversion activities, vanadium surface densities, and VO x species morphology; they also present a straightforward strategy to control surface VO x morphology without requiring complex synthesis protocols.