Support Facet Effects on the Performance of V2O5 -WO3 -CeO2/TiO2 Catalysts for Selective Catalytic Reduction of NO with NH3

Abstract

A micro-catalytic reaction evaluation device, coupled with multiple physicochemical characterization techniques, was employed to study the structure and selective catalytic reduction (SCR) performance of supported V2O5-WO3-CeO2/TiO2 catalysts. TiO2 with preferentially exposed facets served as the catalyst support. The promotional role of CeO2 and the facet effect of the TiO2 support were elucidated, providing critical insights for understanding the SCR mechanism and for the further optimization of catalyst performance. CeO2 was found to enhance the catalytic activity across all V2O5-WO3-CeO2/TiO2 catalysts, irrespective of the predominant facet exposed by the support. Both the NO conversion and N2 selectivity followed the order: V2O5-WO3-CeO2/TiO2-NP{101} > V2O5-WO3-CeO2/TiO2-NL{111} > V2O5-WO3-CeO2/TiO2-NS{001}. Characterization of surface acidity and redox properties revealed that CeO2 modulates catalytic behavior through specific bonding interactions: (i) it attenuates the strength of B acid sites (associated with W6+-OH) via forming O-Ce4+-O-W6+-O linkages, and (ii) it improves the reducibility of V5+ species through Ce4+-O-V5+ bonds. The facet-dependent activity correlated directly with the surface cation vacancy density of the TiO2 supports, measured as 1.7, 1.2 and 1.1 mmol/100 m2 for {101}, {111} and {001} facets, respectively. The {101}-faceted TiO2, possessing the highest vacancy density, fostered the strongest interaction with dispersed V5+, W6+ and Ce4+ ions. This synergistic interaction further optimized the B acid strength and redox properties, ultimately accounting for the superior SCR performance of the V2O5-WO3-CeO2/TiO2-NP{101} catalyst.