MnFeO_x@TiO₂ Nanocages for Selective Catalytic Reduction of NO with NH₃ at Low Temperature

Abstract

Based on Prussian blue analogues (PBAs), using the in situ self-assembly method, MnFeO x @TiO 2 double-walled nanocages with a hollow and porous structure were constructed by annealing the core−shell structure of Mn 3 [Fe(CN) 6 ] 2 •nH 2 O@ Ti(OH) 4 . Compared with the MnFeO x single-walled nanocages without the TiO 2 shell, the MnFeO x @TiO 2 double-walled nanocages exhibited a better catalytic performance in selective catalytic reduction (SCR) with NH 3 at low temperatures, and the NO removal efficiency could reach 80% at 145−260 °C. Establishing the TiO 2 shell layer could effectively improve the adsorption and activation performance of the reactants. Through a series of characterizations, it was confirmed that the MnFeO x @TiO 2 double-walled nanocages possessed a large specific surface area, abundant structural defects, and oxygen vacancies. Besides, the MnFeO x @TiO 2 catalyst had more Mn 4+ species, higher Fe 3+ species, more surface-adsorbed oxygen (O ads ) species, and a strong interaction between MnO x , FeO x , and the TiO 2 shell, which led to better catalytic activity. At the same time, the MnFeO x @TiO 2 double-walled nanocages exhibited satisfactory thermal stability and better H 2 O resistance.

Construction of a Nanorod Structure‐Confined Pt@CeO2 Catalyst by an In‐Situ Encapsulation Strategy for Low‐Temperature Catalytic Oxidation of Toluene

“…The peak values about 530.55±0.03 eV were vested in the surface‐adsorbed oxygen (O β ). The peaks at 532.50 eV (Pt@CeO 2 −R), 532.44 eV (Pt@CeO 2 −B) and 532.46 eV (Pt/CeO 2 −R) were attributed to surface hydroxyl (O γ ) [48] . The proportions of O β over the three samples in Table 1 were 52.2%, 49.5% and 46.75%, respectively.…”

“…The peaks at 532.50 eV (Pt@CeO 2 À R), 532.44 eV (Pt@CeO 2 À B) and 532.46 eV (Pt/CeO 2 À R) were attributed to surface hydroxyl (O γ ). [48] The proportions of O β over the three samples in Table 1 were 52.2%, 49.5% and 46.75%, respectively. It was undeniable that the adsorption oxygen content in the Pt@CeO 2 À R and Pt@CeO 2 À B catalysts was more than that of the Pt/CeO 2 À R catalyst, perhaps because the deposition of Pt NPs on the surface of catalyst inhibited its growth.…”

“…[56] It can be observed that the number of chemisorbed oxygen species were the largest in Pt@CeO 2 À R, which was closely related to the confinement of Pt nanoparticles in CeO 2 . [32] According to some literature, [31,48] a certain amount of O β could promote the circulation of oxygen during the catalytic oxidation process. In addition, due to the presence of Pt 4 + and the confinement of Pt NPs, there was a strong metal-carrier interaction between noble metal nanoparticles and reducible carrier, [54] which induced more oxygen species on the surface, thus significantly reinforcing the activity of Pt@CeO 2 À R catalyst.…”

Fabrication of a multi-dimensional CoFeOx catalyst for the efficient catalytic oxidation elimination of o-dichlorobenzene

“…Generally speaking, Fe 2p is mainly divided into Fe 3+ , Fe 2+ and satellite peaks. 26,45 For 2D/1D CoO x / CoFeO x and 2D CoFeO x catalysts, the Fe 2p 3/2 and Fe 2p 1/2 binding energies are approximately 711.3 AE 0.2 eV and 725.1 AE 0.2 eV for Fe 2+ , and approximately 713.1 AE 0.2 eV and 725.2 AE 0.2 eV for Fe 3+ , respectively. In addition, the contents of Fe 3+ / Fe total on 2D/1D CoO x /CoFeO x and 2D CoFeO x catalysts are 41.25% and 38.42%, respectively.…”

“…The higher Fe 3+ content is favorable for the catalytic oxidation reaction of o-DCB. 40,45 The Fe 3+ content in the 2D/1D CoO x /CoFeO x catalyst is higher than that in the 2D CoFeO x catalyst, which may be one of the reasons that the activity of 2D/1D CoO x /CoFeO x is better than that of the 2D CoFeO x catalyst. The Fe 2p 3/2 and Fe 2p 1/2 binding energies are about 710.1 AE 0.2 and 719.4 AE 0.2 eV on the 2D/1D CoFeO x / CoO x and u-2D/1D CoFeO x /CoO x catalysts, respectively.…”