Number of the records: 1  

Molecular dynamics of preferential adsorption in mixed alkali–halide electrolytes at graphene electrodes

  1. 1.
    0560272 - ÚCHP 2023 RIV US eng J - Journal Article
    Dočkal, J. - Lísal, Martin - Moučka, Filip
    Molecular dynamics of preferential adsorption in mixed alkali–halide electrolytes at graphene electrodes.
    Journal of Chemical Physics. Roč. 157, č. 8 (2022), č. článku 0097425. ISSN 0021-9606. E-ISSN 1089-7690
    R&D Projects: GA ČR(CZ) GA21-27338S
    Institutional support: RVO:67985858
    Keywords : adsorption * molecular dynamics * electrolytes
    OECD category: Physical chemistry
    Impact factor: 4.4, year: 2022
    Method of publishing: Open access with time embargo

    Understanding the microscopic behavior of aqueous electrolyte solutions in contact with graphene and related carbon surfaces is important in electrochemical technologies, such as capacitive deionization or supercapacitors. In this work, we focus on preferential adsorption of ions in mixed alkali–halide electrolytes containing different fractions of Li+/Na+ or Li+/K+ and/or Na+/K+ cations with Cl− anions dissolved in water. We performed molecular dynamics simulations of the solutions in contact with both neutral and positively and negatively charged graphene surfaces under ambient conditions, using the effectively polarizable force field. The simulations show that large ions are often intuitively attracted to oppositely charged electrodes. In contrast, the adsorption behavior of small ions tends to be counterintuitive. In mixedcation solutions, one of the cations always supports the adsorption of the other cation, while the other cation weakens the adsorption of the first cation. In mixed-cation solutions containing large and small cations simultaneously, adsorption of the larger cations varies dramatically with the electrode charge in an intuitive way, while adsorption of the smaller cations changes oppositely, i.e., in a counterintuitive way. For (Li/K)Cl mixed-cation solutions, these effects allow the control of Li+ adsorption by varying the electrode charge, whereas, for LiCl single-salt solutions, Li+ adsorption is nearly independent of the electrode charge. We rationalize this cation–cation lever effect as a result of a competition between three driving forces: (i) direct graphene–ion interactions, (ii) the strong tendency of the solutions to saturate the network of non-covalent intermolecular bonds, and (iii) the tendency to suppress local charge accumulation in any region larger than typical interparticle distances. We analyze the driving forces in detail using a general method for intermolecular bonding based on spatial distribution
    functions and different contributions to the total charge density profiles. The analysis helps to predict whether an ion is more affected by each of the three driving forces, depending on the strength of the ion solvation shells and the compatibility between the contributions of the charge density profiles due to the ion and water molecules. This approach is general and can also be applied to other solutions under different thermodynamic conditions.
    Permanent Link: https://hdl.handle.net/11104/0333260

     
    FileDownloadSizeCommentaryVersionAccess
    0560272_IR.pdf029.4 MBPublisher’s postprintopen-access
     
Number of the records: 1  

  This site uses cookies to make them easier to browse. Learn more about how we use cookies.