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Rationally Tailored Redox Properties of a Mesoporous Mn–Fe Spinel Nanostructure for Boosting Low-Temperature Selective Catalytic Reduction of NOx with NH3
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2020-11-22 , DOI: 10.1021/acssuschemeng.0c05862 Liehao Wei 1 , Xinyong Li 1, 2 , Jincheng Mu 1 , Xinyang Wang 1 , Shiying Fan 1 , Zhifan Yin 1 , Moses O. Tadé 2 , Shaomin Liu 2, 3
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2020-11-22 , DOI: 10.1021/acssuschemeng.0c05862 Liehao Wei 1 , Xinyong Li 1, 2 , Jincheng Mu 1 , Xinyang Wang 1 , Shiying Fan 1 , Zhifan Yin 1 , Moses O. Tadé 2 , Shaomin Liu 2, 3
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Mn–Fe spinel oxides are considered as promising catalysts for low-temperature selective catalytic reduction of NOx with NH3 (NH3-SCR), but the operation temperature window severely suffers from their excessive redox properties. Here, a novel mesoporous nanostructured Mn0.5Fe2.5O4 spinel catalyst (Mn0.5Fe2.5O4-S) with tailored redox properties was synthesized by a facile self-assembly method and applied for NH3-SCR. The morphological structure and physicochemical properties of the as-prepared catalysts were affirmed through comprehensive characterization methods. Compared with the conventional Mn0.5Fe2.5O4 nanoparticle catalyst (Mn0.5Fe2.5O4-P), the Mn0.5Fe2.5O4-S sample exhibited excellent low-temperature De-NOx performance, a wider operation temperature window, lower apparent activation energy, and higher N2 selectivity. The superior catalytic activity of the Mn0.5Fe2.5O4-S catalyst was mainly attributed to its moderate redox properties derived from the unique mesoporous nanostructure with regular dispersed active sites. In situ DRIFTS results indicated that a large amount of −NH2 species were formed on the Mn0.5Fe2.5O4-S due to the appropriate redox properties. Meanwhile, the optimized redox properties could suppress the unwanted NH3 oxidation and thus broaden the temperature window in the middle temperature region. DFT calculation results proved that the Mn0.5Fe2.5O4-S catalyst with the preferentially exposed (220) crystal plane exhibited a lower energy barrier for the activation of NH3 to −NH2. This should be the key factor for intermediate formation and activity enhancement.
中文翻译：
介孔Mn-Fe尖晶石纳米结构的合理定制氧化还原特性，以促进NH 3的低温选择性催化还原NO x
锰铁氧化物尖晶石被认为是有前途的催化剂低温选择性催化还原NO的X与NH 3（NH 3 -SCR），但操作温度窗口从它们的过度氧化还原性能严重受到影响。在此，通过一种简便的自组装方法合成了具有定制氧化还原性能的新型介孔纳米结构Mn 0.5 Fe 2.5 O 4尖晶石催化剂（Mn 0.5 Fe 2.5 O 4 -S）并将其用于NH 3。-SCR。通过综合表征方法确定了所制备催化剂的形态结构和理化性质。与传统的相比，锰0.5铁2.5 ø 4纳米颗粒催化剂（锰0.5铁2.5 ø 4 -P），将Mn 0.5的Fe 2.5 ø 4 -S样品表现出优异的低温脱NO X性能，更宽的操作温度窗口，较低的表观活化能和较高的N 2选择性。Mn 0.5 Fe 2.5 O 4的优异催化活性-S催化剂主要归因于其中等的氧化还原性质，该性质源自具有规则分散的活性位点的独特的中孔纳米结构。原位DRIFTS结果表明，由于适当的氧化还原性质，在Mn 0.5 Fe 2.5 O 4 -S上形成了大量的-NH 2物种。同时，优化的氧化还原特性可以抑制有害的NH 3氧化，从而拓宽了中温区的温度范围。DFT计算结果表明，优先暴露（220）晶面的Mn 0.5 Fe 2.5 O 4 -S催化剂对NH的活化能垒较低。3至-NH 2。这应该是中间体形成和活性增强的关键因素。
更新日期：2020-12-07
中文翻译：
介孔Mn-Fe尖晶石纳米结构的合理定制氧化还原特性，以促进NH 3的低温选择性催化还原NO x
锰铁氧化物尖晶石被认为是有前途的催化剂低温选择性催化还原NO的X与NH 3（NH 3 -SCR），但操作温度窗口从它们的过度氧化还原性能严重受到影响。在此，通过一种简便的自组装方法合成了具有定制氧化还原性能的新型介孔纳米结构Mn 0.5 Fe 2.5 O 4尖晶石催化剂（Mn 0.5 Fe 2.5 O 4 -S）并将其用于NH 3。-SCR。通过综合表征方法确定了所制备催化剂的形态结构和理化性质。与传统的相比，锰0.5铁2.5 ø 4纳米颗粒催化剂（锰0.5铁2.5 ø 4 -P），将Mn 0.5的Fe 2.5 ø 4 -S样品表现出优异的低温脱NO X性能，更宽的操作温度窗口，较低的表观活化能和较高的N 2选择性。Mn 0.5 Fe 2.5 O 4的优异催化活性-S催化剂主要归因于其中等的氧化还原性质，该性质源自具有规则分散的活性位点的独特的中孔纳米结构。原位DRIFTS结果表明，由于适当的氧化还原性质，在Mn 0.5 Fe 2.5 O 4 -S上形成了大量的-NH 2物种。同时，优化的氧化还原特性可以抑制有害的NH 3氧化，从而拓宽了中温区的温度范围。DFT计算结果表明，优先暴露（220）晶面的Mn 0.5 Fe 2.5 O 4 -S催化剂对NH的活化能垒较低。3至-NH 2。这应该是中间体形成和活性增强的关键因素。
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