Influence of deposition order of dual active components on the NH3-SCO performance of the bimetallic Pt–V system supported on TiO2

Abstract

The Pt–V bimetallic catalytic system may be a promising alternative to noble metal catalysts for selective catalytic oxidation (SCO) of NH₃. But it is challenging to improve the NH₃ conversion activity and N₂ selectivity, as well as cost-economy. Herein, the influence of the deposition order of V and Pt components on NH₃-SCO performance was investigated with constant loadings of 0.5 wt% V and 0.04 wt% Pt. The catalytic performance of the Pt–V system significantly depended on the combination mode between VO_x and Pt species. The V_0.5/Pt_0.04/TiO₂ catalyst exhibited outstanding NH₃-SCO performance, giving complete NH₃ conversion and 80.2% N₂ selectivity at 225 °C. This was ascribed to a preferable synergistic effect between the upper layer of VO_x species and the lower layer of Pt species supported on TiO₂. This led to more abundant Pt⁰ species in the lower layer, which was favorable for oxidizing the diffused NH₃ efficiently into N₂, H₂O and some NO_x. The generated NO_x would further react with fresh NH₃ in an efficient way under the action of VO_x species in the upper layer via selective catalytic reduction (SCR) reactions owing to the excellent redox ability of the V_0.5/Pt_0.04/TiO₂ catalyst. –NH₂ species and nitrate species were the main intermediates participating in the NH₃-SCO reactions over the V_0.5/Pt_0.04/TiO₂ catalyst.