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

It is still a great challenge for the selective catalytic reduction (SCR) of NOx 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 NOx 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.