Lee Sang Soo, Park Changyong, Sturchio Neil C, Fenter Paul
Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
HP-CAT, X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
J Phys Chem Lett. 2020 May 21;11(10):4029-4035. doi: 10.1021/acs.jpclett.0c00808. Epub 2020 May 7.
Ion adsorption at solid-water interfaces is commonly described by interactions between specific surface sites and adsorbed ions in classical models. However, energetic contributions from non-site-specific ion-ion interactions have been less well understood. Here, we report nonclassical behaviors observed during competitive adsorption between Sr and Na/Rb at the negatively charged muscovite mica (001)-water interface, revealing apparent controls of adsorbed ion speciation over the interfacial reactivity. In the absence of competing cations, Sr adsorbs in approximately equivalent proportions of inner-sphere and outer-sphere complexes, whereas it adsorbs predominantly as an outer-sphere complex in the presence of Na/Rb. This transformation of adsorbed Sr speciation significantly decreases its adsorption strength, as indicated by the ∼15-fold shift in the Sr adsorption edge concentration, compared to that calculated from a classical Langmuir isotherm model developed on the basis of site-specific interactions. These observations highlight the importance of non-site-specific interactions in controlling the energetics of chemical reactions at the charged interface.
在经典模型中，固体 - 水界面处的离子吸附通常通过特定表面位点与吸附离子之间的相互作用来描述。然而，非位点特异性离子 - 离子相互作用对能量的贡献尚未得到很好的理解。在此，我们报告了在带负电荷的白云母云母（001） - 水界面上Sr与Na/Rb竞争吸附过程中观察到的非经典行为，揭示了吸附离子形态对界面反应性的明显控制。在没有竞争阳离子的情况下，Sr以内层和外层配合物的大致相等比例吸附，而在存在Na/Rb的情况下，它主要以外层配合物的形式吸附。吸附的Sr形态的这种转变显著降低了其吸附强度，与基于位点特异性相互作用开发的经典朗缪尔等温线模型计算的结果相比，Sr吸附边缘浓度有大约15倍的变化。这些观察结果突出了非位点特异性相互作用在控制带电界面化学反应能量方面的重要性。
