阳离子Cu n +（n = 4-7）团簇上H 2吸附的红外光谱表征,The Journal of Physical Chemistry A

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阳离子Cu _n⁺（n = 4-7）团簇上H ₂吸附的红外光谱表征
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2021-03-31 , DOI: 10.1021/acs.jpca.0c11527
Olga V. Lushchikova ₁ , Hossein Tahmasbi ₂ , Stijn Reijmer ₁ , Rik Platte ₂ , Jörg Meyer ₂ , Joost M. Bakker ₁

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通过红外多光子离解（IRMPD）光谱记录了与氢分子络合的阳离子铜簇Cu _n⁺（n = 4-7）的IR光谱。为此，铜团簇通过激光烧蚀产生并与H ₂和D ₂反应在流管式反应通道中。使用由自由电子激光器提供的IR光进行腔内实验（FELICE）照射形成的复合物。通过利用同位素引起的振动带位移，并将其与候选结构的密度泛函理论计算的光谱进行比较，来解释光谱。已通过最小跳频方法从全局采样中获得了结构候选对象，并在半局部（PBE）和混合（PBE0）功能级别上计算了光谱。记录了[5Cu，2H / 2D] ⁺的最高质量的光谱，我们发现半局部官能团为能量最低的异构体提供了更好的一致性。氢与铜簇的相互作用在很大程度上取决于它们的大小。Cu ₅^+的结合能最大，这与观察到的主要为离解性吸附密切相关。由于解离的H ₂和D ₂与Cu ₄^+的结合能较小，因此根据Evans-Polanyi原理，也观察到大量的分子吸附。Cu ₄⁺和Cu ₅^+的过渡态计算证实了这一点。，这表明，氢解离不妨碍通过对Cu的吸热反应阻挡₅⁺，并通过对Cu轻微吸热屏障₄⁺。对于Cu ₆⁺和Cu ₇⁺，很难得出明确的结论，因为无法明确地将IR光谱分配给结构。

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IR Spectroscopic Characterization of H2 Adsorption on Cationic Cun+ (n = 4–7) Clusters

IR spectra of cationic copper clusters Cu_n⁺ (n = 4–7) complexed with hydrogen molecules are recorded via IR multiple-photon dissociation (IRMPD) spectroscopy. To this end, the copper clusters are generated via laser ablation and reacted with H₂ and D₂ in a flow-tube-type reaction channel. The complexes formed are irradiated using IR light provided by the free-electron laser for intracavity experiments (FELICE). The spectra are interpreted by making use of isotope-induced shifts of the vibrational bands and by comparing them to density functional theory calculated spectra for candidate structures. The structural candidates have been obtained from global sampling with the minima hopping method, and spectra are calculated at the semilocal (PBE) and hybrid (PBE0) functional level. The highest-quality spectra have been recorded for [5Cu, 2H/2D]⁺, and we find that the semilocal functional provides better agreement for the lowest-energy isomers. The interaction of hydrogen with the copper clusters strongly depends on their size. Binding energies are largest for Cu₅⁺, which goes hand in hand with the observed predominantly dissociative adsorption. Due to smaller binding energies for dissociated H₂ and D₂ for Cu₄⁺, also a significant amount of molecular adsorption is observed as to be expected according to the Evans–Polanyi principle. This is confirmed by transition-state calculations for Cu₄⁺ and Cu₅⁺, which show that hydrogen dissociation is not hindered by an endothermic reaction barrier for Cu₅⁺ and by a slightly endothermic barrier for Cu₄⁺. For Cu₆⁺ and Cu₇⁺, it was difficult to draw clear conclusions because the IR spectra could not be unambiguously assigned to structures.

更新日期：2021-04-15

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