Design strategies for SCR catalysts with improved N2 selectivity: the significance of nano-confining effects by titanate nanotubes

Abstract

Copper has been investigated as a promising alternative for SCR reactions. However, most Cu-based catalysts supported on zeolites, alumina or titania produced a certain amount of undesired N₂O by-product. Herein, we report a strategy to tune the redox properties of copper oxides via confinement within titanate nanotubes (Cu/TNTs) and investigate their SCR activity as well as the N₂ selectivity. The Cu/TNT catalyst showed an excellent NO reduction performance (above 90%) in the temperature window of 300–450 °C and the N₂ selectivity could exceed 98% among the whole reaction temperature range of 150–470 °C, with a negligibly low concentration of N₂O being detected. After systematic characterizations, the tuning of the chemical state of copper and oxygen, the remarkable adsorption capability, the accelerated oxidation of Cu⁺ to Cu²⁺, the lower level of NH₃ oxidation and ultimately the tuning of redox properties were discovered. This work could provide a new approach to design SCR catalysts with superior catalytic reduction performance as well as excellent N₂ selectivity.