Electron donation mechanism of superior Cs-supported oxides for catalytic soot combustion
Electron donation mechanism of superior Cs-supported oxides for catalytic soot combustion
复制标题
优质铯负载氧化物催化烟灰燃烧的电子供给机制
DOI：
10.1016/j.cej.2017.12.146
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发表时间：
2018-04-01
影响因子：
15.1
通讯作者：
Cao, Xiaoming
中科院分区：
文献类型：
--
作者：
Li, Qian;Xin, Ying;Cao, Xiaoming
柴油发动机排放的碳烟颗粒会造成严重的环境和健康问题。碱金属氧化物催化燃烧脱除碳烟是最有前途的后处理技术之一，因为它不使用贵金属。然而，碱金属氧化物对气态氧和/或烟尘的活化机理尚不清楚。据报道，Cs负载的典型氧化物对碳烟燃烧的催化性能优于研究最多的K负载氧化物。活性物种被表征为Cs2O，而与K负载催化剂一样，烯酮仍被区分为反应中间体。Cs2O更容易给O-2电子，而K2O给电子更容易，导致更多的活性氧物种和更高的电荷密度。另一方面，煤烟在Cs2O表面的化学吸附比在K2O表面更容易通过煤烟边缘的含氧基团被活化，从而导致更多的电子从Cs2O提供给煤烟。这些理论计算结果得到了碳烟燃烧的原位红外光谱的进一步证实。对给电子机理的理解有助于理解碱金属氧化物催化碳烟燃烧的本质。
Soot particulates from diesel engines cause serious environmental and health problems. Catalytic combustion removal of soot by alkali metal oxides is one of the most promising aftertreatment techniques because no precious metals are used. However, the activation mechanism of gaseous oxygen and/or soot by alkali metal oxides remains unclear. Here, Cs-supported typical oxides were reported to exhibit superior catalytic performance for soot combustion to the most studied K-supported counterparts. The active species were characterized as Cs2O, whilst ketene was still distinguished as the reaction intermediate as in the case of the K-supported catalysts. The easier electron donation from Cs2O to O-2 than from K2O results in the more active oxygen species with higher charge density. On the other hand, soot activation by chemisorption on the Cs2O surface is easier than on the K2O surface via the oxygen-containing group at the edge of soot, leading to more electrons donated from Cs2O to soot. These theoretical calculation results were further confirmed by in situ IR of soot combustion. The understanding of the electron donation mechanism provides an insight into the essence of soot combustion catalyzed by alkali metal oxides.