Anatase TiO2 nanosheets (TiO2-NS) and nanospindles (TiO2-NSP) have been successfully prepared with F– and glacial acetic acid as structure-directing agents, respectively. The Fe2O3/TiO2-NS and Fe2O3/TiO2-NSP nanocatalysts were prepared by a wet incipient impregnation method with a monolayer amount of Fe2O3. All the catalysts were employed for the selective catalytic reduction of NO with NH3 (NH3-SCR) in order to understand the morphology-dependent effects. It is interesting that the Fe2O3/TiO2-NS nanocatalyst exhibited better removal efficiency of NO x in the temperature range of 100–450 °C, which was attributed to more oxygen defects and active oxygen, acid sites, as well as adsorbed nitrate species based on Raman spectra, XPS, NH3-TPD, NO+O2-TPD, and in situ DRIFTS. The density functional theory (DFT) method was used to clarify the NO and NH3 adsorption abilities over the catalyst models of Fe2O3/TiO2{001} and Fe2O3/TiO2{101}. The results showed that the NH3 adsorption energy over the TiO2{001} (−2.00 eV) was lower than that over TiO2{101} (−1.21 eV), and the NO adsorption energy over TiO2{001} (−1.62 eV) was also lower than that over TiO2{101} (−0.29 eV), which agreed well with the experimental results that Fe2O3/TiO2-NS achieved higher catalytic activity than Fe2O3/TiO2-NSP for NH3-SCR of NO. In addition, the rapid electron transfer and regeneration of Fe3+ on the {001} facet of Fe2O3/TiO2-NS also promoted the NH3-SCR reaction efficiency. This work paves a way for understanding the facet–activity relationship of Fe2O3/TiO2 nanocatalysts in the NH3-SCR reaction.

Size effects have been recognized to promote the catalytic activity and selectivity of metal oxide particles. So far, limited works and studies are conducted to investigate the size effect of metal oxide with the tailored shape in the selective catalytic reduction of NO with NH (NH-SCR). Herein, the MnO-FeO nanocage catalysts with varied scales (0.25, 0.5, 1, and 2 μm) were synthesized via a Prussian blue analogue (PBA)-derived method and used for NH-SCR of NO. By preforming a series of the activity tests over the nanocages with different scales, the NH-SCR activity of 0.5 μm MnO-FeO nanocage catalysts exhibits the highest deNO activity in the temperature range of 80-200 °C owing to more preferable physical and chemical properties. It has been demonstrated that there is a strong interaction among Mn and Fe cations in the 0.5 μm MnO-FeO nanocages. Moreover, the H-TPR and XPS analysis prove 0.5 μm nanocages exhibit excellent redox properties, which contribute to the higher conservation of NO. Through the DFT studies, it is also demonstrated that the 0.5 μm MnO-FeO nanocage catalysts could provide more preferable electronic charge, which gives rise to the varied adsorption behavior of the NH species and NO species compared to the nanocages with other scales. The in situ DRIFTs were also employed to evaluate the adsorption status of NH with NO species over MnO-FeO nanocage catalysts with varied scales. Finally, the scale-activity relationship of the MnO-FeO nanocage catalysts and their corresponding activities are also established. The deep insight into the scale-activity relationship of the PBA-derived MnO-FeO nanocage catalyst paves the way for developing and designing highly efficient Mn-based catalyst at lower temperature.

In this work, mesoporous TiO2 spheres supported MnCeW mixed oxide catalysts (MnCeW/m-TiO2) for selective catalytic reduction of NO x with NH3 were prepared by a wet impregnation method. It is interesting that the MnCeW/m-TiO2 catalysts exhibited excellent SCR activity and N2 selectivity in a wide temperature range, even under the high gas hourly space velocity. From in situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTs) studies of desorption, it could be concluded that the addition of tungsten brought about more Brønsted acid sites and reduced the energy barrier of NO x species adsorbed on the surface. At high temperature range, there were still some Brønsted acid sites and NO x species including bidentate nitrate and nitro compounds in MnCeW/m-TiO2, therefore more intermediates could take part in the SCR reactions as well as better catalytic performance. Besides, the in situ DRIFTs of transient reactions indicated that the formed NH3 species and NO x species of MnCeW/m-TiO2 were more reactive due to the promotional effects of tungsten. A series of traditional characterizations also revealed the promotional effects of tungsten for surface active elements, catalytic redox properties, and acid sites of NH3 adsorption. In a word, all the results confirmed that the introduction of W could enhance active NH3 and NO x species as well as surface active elements, thus contributing to the catalytic performance. The present investigations may open a path for design and application of catalysts with outstanding catalytic activity and selectivity.

Hollandite Mn–Ti oxide promoted Cu-SAPO-34 catalysts exhibited outstanding deNOx performance and excellent resistance against alkali metal poisoning.