SO2-Tolerant catalytic reduction of NOx by confining active species in TiO2 nanotubes

Abstract

It is still a great challenge for the selective catalytic reduction (SCR) of NO_x in the presence of SO₂. Herein, active Cu species confined in TiO₂ nanotubes (TiO₂ NTs) as SCR catalysts were originally developed and proven to possess excellent SO₂ tolerance for NO_x reduction. Most of the active Cu species were confined in TiO₂ NTs, which possessed a larger specific surface area, thus accelerating the redox cycle and increasing the Lewis acidity of the catalyst. Moreover, the special confinement effect of TiO₂ NTs on Cu species ensured more active Cu⁺ sites emergence. Remarkably, the electron-rich state of active Cu⁺ sites greatly weakened the SO₂ adsorption and oxidation process, and thus the active components were immunized from SO₂ poisoning. Therefore, the prominent SO₂ resistance of SCR catalysts was realized via the special structure–activity relationship in that the surface electron cloud density of Cu was effectively adjusted by the confinement effect of TiO₂ NTs. This work provides a novel way for the development of highly efficient SCR catalysts with excellent SO₂ tolerance.