Capacitive electronic metal-support interactions: Outer surface charging of supported catalyst particles
Capacitive electronic metal-support interactions: Outer surface charging of supported catalyst particles
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DOI：
10.1103/physrevb.96.165405
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发表时间：
2017-10-04
影响因子：
3.7
通讯作者：
Kramer, Denis
中科院分区：
文献类型：
--
作者：
Binninger, Tobias;Schmidt, Thomas J.;Kramer, Denis
催化中的电子金属-支撑相互作用（EMSI）通常是根据支撑材料和支撑金属催化剂颗粒之间的电子转移来合理化的。然而，这种一般观点并不能完全解释实验观察到的金属纳米颗粒催化剂的EMSI，因为金属的强电荷筛选应该局部地将与载体的直接电子相互作用的影响限制在催化剂载体界面（CSI）上，除了周长之外，催化反应物在很大程度上是无法进入的。本文针对纳米尺度的催化剂颗粒提出了电容性EMSI的概念，其中电子平衡导致催化活性外表面（CAOS）的远程充电，绕过预期的强金属电荷屏蔽，这一点通过静电和密度泛函理论模拟得到证实和量化，揭示了催化剂颗粒对支撑表面的覆盖程度有很强的依赖性。这种远程电荷转移导致CAOS局部功函数的转移。为了描述催化结果，提出了用“d带+功函数”来修正d带理论。此外，在CAOS尺度上，远端催化位点的充电与周围介质的相对介电常数有关，并得出结论，EMSI可以产生惊人的强大影响，特别是在存在强极化介质的情况下。
Electronic metal-support interactions (EMSI) in catalysis are commonly rationalized in terms of an electron transfer between supportmaterial and supportedmetal catalyst particles. This general perspective, however, cannot fully explain experimentally observed EMSI for metallic nanoparticulate catalysts, because the strong charge screening of metals should locally confine effects of direct electronic interaction with the support to the catalystsupport interface (CSI), which, apart from the perimeter, is largely inaccessible for catalysis reactants. The concept of capacitive EMSI is proposed here for catalyst particles at the nanometer scale, where electronic equilibration results in a long-range charging of the catalytically active outer surface (CAOS) bypassing the expected strong metallic charge screening, which is confirmed and quantified by electrostatic and density functional theory simulations revealing a strong dependence on the coverage of the support surface with catalyst particles. This long-range charge transfer leads to a shift of the local work function at the CAOS. In order to describe the catalytic consequences, an amendment of d-band theory in terms of 'd-band + work function' is proposed. Furthermore, the charging of remote catalytic sites at the CAOS scales with the relative dielectric constant of the surrounding medium, and it is concluded that EMSI can have surprisingly strong influence especially in the presence of a strongly polarizable dielectric.