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Tuning electronic states of catalytic sites enhances SCR activity of hexagonal WO3 by Mo framework substitution

机译：优化催化网站的电子态提高可控硅活动六角WO3的莫框架替换

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摘要

Selective catalytic reduction (SCR) of NO with NH3 essentially proceeds via redox cycles, in which electrons transfer between reactants and catalytically active sites (CASs). Hence, the electronic states of CASs play a crucial role in determining the SCR activity of catalysts. Herein, we tune the electronic structures of CASs via substitution of the hexagonal WO3 framework by Mo (Mo-HWO). The resulting Mo-HWO catalyst shows a high NO conversion of 80% at 350 degrees C at a gas hourly space velocity of 32000 h(-1), in the presence of high-concentration SO2 (2700 mg m(-3)) and 10 vol% H2O. Various characterization results demonstrate that the CASs responsible for NH3 adsorption and activation are located at the tunnel openings, i.e., the (001) top-facets of Mo-HWO nanorods. The framework substitution by Mo reduces the bandgap between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals by hybridizing W and Mo cations with their bridging oxygen ions, thus making the electron transfers in SCR redox cycles relatively easy and leading to improved catalytic activity. This work could assist the rational design of catalysts by tuning the electronic states of CASs.
机译：选择性催化还原(SCR)与NH3的本质上收益通过氧化还原循环,反应物和之间的电子转移催化地活跃网站(CASs)。电子的卡斯起到至关重要的作用确定SCR催化剂的活性。在此,我们优化卡斯的电子结构通过替换的六角WO3框架由密苏里州(Mo-HWO)。显示了一个高没有80%至350度的转变C的气体时空速32000 h (1),在高浓度二氧化硫(2700mg m(3))和10卷% H2O。表征结果表明,卡斯NH3吸附和负责激活位于地道入口,即(001)top-facets Mo-HWO纳米棒。莫减少了框架替换最高占据分子之间的能带占据分子轨道和最低的轨道通过杂交W和密苏里州的阳离子他们的桥接氧离子,从而使电子转移在可控硅氧化还原周期相对简单,导致催化活性提高。这项工作可能协助的理性设计通过调优的电子态催化剂卡斯。

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