Tuning the charge states of CrW2O9 clusters deposited on perfect and defective MgO(001) surfaces with different color centers: A comprehensive DFT study
Tuning the charge states of CrW2O9 clusters deposited on perfect and defective MgO(001) surfaces with different color centers: A comprehensive DFT study
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调整沉积在具有不同色心的完美和有缺陷的 MgO(001) 表面上的 CrW2O9 团簇的电荷态：全面的 DFT 研究
DOI：
10.1063/1.4947549
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发表时间：
2016
影响因子：
4.4
通讯作者：
Zhang Yongfan
中科院分区：
文献类型：
--
作者：
Zhu Jia;Zhang Hui;Tong Yawen;Wang Chengxing;Wang Bin;Huang Xin;Zhang Yongfan
用密度泛函理论方法研究了双金属氧化物CrW{sub2}O{sub9}团簇分别以F{subS}{sup 0}、F{subS}{sup+}和F{subS}{sup2+}三种不同色心的完美表面和缺陷表面上的结构和电子性质。结果表明，分散的CrW{sub2}O{sub9}团簇的构型、吸附能、电荷转移和成键方式对F{subS}中心的电荷态很敏感。与气相结构相比，负载在缺陷表面上的CrW{sub2}O{sub9}团簇发生了显著的扭曲，表现出不同的链结构。在完美的MgO表面上，团簇的沉积不涉及明显的电荷转移，而在缺陷的MgO(001)表面上，情况则截然不同，其中有明显的电子从表面转移到团簇。有趣的是，这种效应在富电子氧空位(F{SUB S}{sup 0}中心)比贫电子氧空位(F{subS}{sup+}和F{subS}{sup 2+}中心)更为显著。此外，我们的工作揭示了所有F{sub2}-S}中心的自旋密度优先集中在铬原子而不是W原子周围的渐进式Brnsted酸中心，这表明相对于W{sub3}O{sub9}簇，在缺陷的MgO(001)表面上的CrW{sub2}O{sub9}簇具有更好的催化活性。
The structures and electronic properties of bimetallic oxide CrW{sub 2}O{sub 9} clusters supported on the perfect and defective MgO(001) surfaces with three different color centers, F{sub S}{sup 0}, F{sub S}{sup +}, and F{sub S}{sup 2+} centers, respectively, have been investigated by density functional theory calculations. Our results show that the configurations, adsorption energies, charge transfers, and bonding modes of dispersed CrW{sub 2}O{sub 9} clusters are sensitive to the charge states of the F{sub S} centers. Compared with the gas-phase configuration, the CrW{sub 2}O{sub 9} clusters supported on the defective surfaces are distorted dramatically, which exhibit different chain structures. On the perfect MgO surface, the depositions of clusters do not involve obvious charge transfer, while the situation is quite different on the defective MgO(001) surfaces in which significant electron transfer occurs from the surface to the cluster. Interestingly, this effect becomes more remarkable for electron-rich oxygen vacancies (F{sub S}{sup 0} center) than that for electron-poor oxygen vacancies (F{sub S}{sup +} and F{sub S}{sup 2+} centers). Furthermore, our work reveals a progressive Brønsted acid sites where spin density preferentially localized around the Cr atoms not the W atoms for all kinds of F{sub S}-centers, indicating the better catalytic activities can be expected for CrW{sub 2}O{sub 9} cluster on defective MgO(001) surfaces with respect to the W{sub 3}O{sub 9} cluster.