International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China.
Published: February 2024
AI Article Synopsis
Article Abstract
Condensation and arrangement of ions at water-solid interfaces are of great importance in the formation of electrical double layers (EDL) and the transport of ions under a confined geometry. So far, the microscopic understanding of interfacial ion configurations is still far from complete, especially when the local ion concentration is high and ion-ion interactions become prominent. In this study, we directly visualized alkali metal cations within the hydrogen-bonding network of water on graphite and Cu(111)-supported graphene surfaces, using qPlus-based noncontact atomic force microscopy (NC-AFM). We found that the codeposition of the alkali cations and water molecules on the hydrophobic graphite surface leads to the formation of an ion-doped bilayer hexagonal ice (BHI) structure, where the ions are repelled from each other and scattered in a disordered distribution. In contrast, the hydrated alkali cations aggregate in one dimension on the more hydrophilic graphene/Cu(111) surface, forming a nematic state with a long-range order. Such a nematic state arises from the delicate interplay between water-ion and water-water interactions under surface confinement. These results reveal the high sensitivity of ion-ion interactions and ionic ordering to the surface hydrophobicity and hydrophilicity.
Highly concentrated salt solutions are promising electrolytes for battery applications due to their low flammability, their high thermal stability, and their good compatibility with electrode materials. Understanding transport processes in highly concentrated electrolytes is a challenging task, since strong ion-ion and ion-solvent interactions lead to highly correlated movements on the microscopic scale. Here, we use an experimental overdetermination method to obtain accurate Onsager transport coefficients for concentrated binary electrolytes composed of either sulfolane (SL) or dimethyl carbonate (DMC) as solvent and either LiTFSI or LiFSI as salt.
Lattice-based mean-field models of ionic liquids neglect charge discreteness and ion correlations. To address these limitations, we propose separating the short-range and long-range parts of the electrostatic interaction by truncating the Coulomb potential below a fixed distance that is equal to or slightly larger than that between neighboring ions. Interactions and correlations between adjacent ions can then be modeled explicitly, whereas longer-ranged electrostatic interactions are captured on the mean-field level.
Department of Instrumentation and Analytical Chemistry, CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China.
As water-saturated polymer networks, the easy water loss of hydrogels directly affects their end-use applications. Minimizing the ratio of free water and increasing the ratio of bound water in the gel system has become key to extending the service life. In this work, an ionogel is prepared that effectively regulates the proportion of free water and bound water through the formation of wrinkle angles by the hydrophilic and hydrophobic chains in the gel system and the non-volatile nature of the ionic liquid.
The Madrid-2019 force field was recently developed to perform simulations of electrolytes in water. The model was specifically parameterized for TIP4P/2005 water and uses scaled charges for the ions. In this work, we test the compatibility of the Madrid-2019 force field with another water model: TIP4P/Ice.
Memristors that mimic brain functions are crucial for energy-efficient neuromorphic devices. Ion channels that emulate biological synapses are still in the early stages of development, especially the tunability of memory states. Here, we demonstrate that cations such as K, Na, Ca, and Al intercalated in the interlayer spaces of vermiculite result in highly confined channels of size 3-5 Å.
