Souna Amanda J, Motevaselian Mohammad H, Polster Jake W, Tran Jason D, Siwy Zuzanna S, Aluru Narayana R, Fourkas John T
Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA.
Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61820, USA.
Phys Chem Chem Phys. 2024 Feb 22;26(8):6726-6735. doi: 10.1039/d3cp05712g.
The nanoscale organization of electrolyte solutions at interfaces is often described well by the electrical double-layer model. However, a recent study has shown that this model breaks down in solutions of LiClO in acetonitrile at a silica interface, because the interface imposes a strong structuring in the solvent that in turn determines the preferred locations of cations and anions. As a surprising consequence of this organisation, the effective surface potential changes from negative at low electrolyte concentration to positive at high electrolyte concentration. Here we combine previous ion-current measurements with vibrational sum-frequency-generation spectroscopy experiments and molecular dynamics simulations to explore how the localization of ions at the acetonitrile-silica interface depends on the sizes of the anions and cations. We observe a strong, synergistic effect of the cation and anion identities that can prompt a large difference in the ability of ions to partition to the silica surface, and thereby influence the effective surface potential. Our results have implications for a wide range of applications that involve electrolyte solutions in polar aprotic solvents at nanoscale interfaces.
界面处电解质溶液的纳米级组织通常可以用电双层模型很好地描述。然而，最近的一项研究表明，在二氧化硅界面的乙腈中LiClO溶液中，该模型失效了，因为界面在溶剂中施加了强烈的结构，这反过来又决定了阳离子和阴离子的优先位置。作为这种组织的一个令人惊讶的结果，有效表面电位从低电解质浓度下的负值变为高电解质浓度下的正值。在这里，我们将先前的离子电流测量与振动和频产生光谱实验以及分子动力学模拟相结合，以探索乙腈-二氧化硅界面处离子的定位如何取决于阴离子和阳离子的大小。我们观察到阳离子和阴离子身份的强烈协同效应，这可能导致离子分配到二氧化硅表面的能力有很大差异，从而影响有效表面电位。我们的结果对广泛涉及纳米级界面处极性非质子溶剂中电解质溶液的应用具有重要意义。
