Morphology-dependent performance of Zr–CeVO4/TiO2 for selective catalytic reduction of NO with NH3

Abstract

A novel Zr–CeVO₄/TiO₂ catalyst was developed for the selective catalytic reduction (SCR) of NO with NH₃. Both TiO₂ nanosheets (TiO₂-NS) and nanoparticles (TiO₂-NP) with different crystal facets were used as supports for the catalyst. It was found that the TiO₂-NS-supported catalyst showed much better activity, stability and H₂O/SO₂ durability than the TiO₂-NP-supported catalyst. In particular, the catalyst loading amount was much lower than those of previously reported vanadate-based SCR catalysts. The crystal structures and morphologies were analysed by X-ray diffraction (XRD), Raman spectroscopy and (high-resolution) transmission electron microscopy ((HR)TEM). The redox properties, surface active species and acid sites of the catalysts were investigated through hydrogen temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS), ammonia and nitrogen oxide temperature-programmed desorption (NH₃-TPD and NO_x-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTs) experiments. The improved activity at lower temperature was due to the presence of more active oxygen species and Brønsted acid sites, as well as the formation of NO₂ on the surface of the TiO₂ nanosheets which have exposed (001) facets. The enhanced stability and H₂O/SO₂ durability of Zr–CeVO₄/TiO₂-NS was due to the limited formation of NH₄NO₃ and (NH₄)₂SO₄/NH₄HSO₄. The excellent low operation temperature, low vanadium content and absence of WO₃(MoO₃) in this catalyst indicated that it has promising potential as a SCR catalyst for practical applications.