Rationally Designed Porous MnOx–FeOx Nanoneedles for Low-Temperature Selective Catalytic Reduction of NOx by NH3,ACS Applied Materials & Interfaces

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Rationally Designed Porous MnOx–FeOx Nanoneedles for Low-Temperature Selective Catalytic Reduction of NOx by NH3
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2017-05-03 00:00:00 , DOI: 10.1021/acsami.7b00739
Zhaoyang Fan ₁ , Jian-Wen Shi ₁ , Chen Gao ₁ , Ge Gao ₁ , Baorui Wang ₁ , Chunming Niu ₁

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In this work, a novel porous nanoneedlelike MnO_x–FeO_x catalyst (MnO_x–FeO_x nanoneedles) was developed for the first time by rationally heat-treating metal–organic frameworks including MnFe precursor synthesized by hydrothermal method. A counterpart catalyst (MnO_x–FeO_x nanoparticles) without porous nanoneedle structure was also prepared by a similar procedure for comparison. The two catalysts were systematically characterized by scanning and transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, ammonia temperature-programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFT), and their catalytic activities were evaluated by selective catalytic reduction (SCR) of NO_x by NH₃. The results showed that the rationally designed MnO_x–FeO_x nanoneedles presented outstanding low-temperature NH₃-SCR activity (100% NO_x conversion in a wide temperature window from 120 to 240 °C), high selectivity for N₂ (nearly 100% N₂ selectivity from 60 to 240 °C), and excellent water resistance and stability in comparison with the counterpart MnO_x–FeO_x nanoparticles. The reasons can be attributed not only to the unique porous nanoneedle structure but also to the uniform distribution of MnO_x and FeO_x. More importantly, the desired Mn⁴⁺/Mnⁿ⁺ and O_α/(O_α + O_β) ratios, as well as rich redox sites and abundant strong acid sites on the surface of the porous MnO_x–FeO_x nanoneedles, also contribute to these excellent performances. In situ DRIFT suggested that the NH₃-SCR of NO over MnO_x–FeO_x nanoneedles follows both Eley–Rideal and Langmuir–Hinshelwood mechanisms.

中文翻译：

合理设计的MnO _x –FeO _x纳米多孔纳米管，用于低温选择性催化NH ₃还原NO _x

在这项工作中，通过合理地热处理包括水热法合成的MnFe前驱体的金属有机骨架，首次开发了一种新型的多孔纳米针状MnO _x -FeO _x催化剂（MnO _x -FeO _x纳米针）。对应的催化剂（MnO _x –FeO _x还通过类似的程序制备了不具有多孔纳米针结构的纳米颗粒）。通过扫描和透射电子显微镜，X射线衍射，热重分析，X射线光电子能谱，氢程序升温还原，氨程序升温脱附和原位漫反射红外傅里叶变换光谱对这两种催化剂进行了系统表征。原位DRIFT），和它们的催化活性通过选择性催化还原（SCR）的评价NO _X由NH ₃。结果表明，合理设计的MnO _x –FeO _x纳米针具有出色的低温NH ₃ -SCR活性（100％NO _x与MnO _x -FeO _x相比，在120至240°C的宽温度范围内转化），对N _2的高选择性（从60至240°C的N ₂选择性接近100％）以及出色的耐水性和稳定性纳米粒子。原因不仅可以归因于独特的多孔纳米针结构，还可以归因于MnO _x和FeO _x的均匀分布。更重要的是，在多孔MnO _x表面上，所需的Mn ⁴⁺ / Mn ⁿ⁺和_Oα /（_Oα + _Oβ）比以及丰富的氧化还原位点和丰富的强酸位点-FeO _x纳米针也有助于实现这些出色的性能。原位DRIFT表明MnO _x –FeO _x纳米针上的NO的NH ₃ -SCR遵循Eley–Rideal和Langmuir–Hinshelwood机理。

更新日期：2017-05-09

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