Title: Confinement effects on the solvation structure of solvated alkaline metal cations in a single-digit 1T-MoS₂ nanochannel: A first-principles study

Abstract

Confinement plays an important role in determining ion transport in porous materials, which, in turn, may influence the performance of many energy storage and desalination devices. In this work, we combined density functional theory (DFT) with an implicit solvation model and ab initio molecular dynamics (AIMD) to investigate the effects of nanoconfinement on several solvated alkaline metal cations in a single-digit 1T-MoS₂ nanochannel. Our DFT calculations with a solvation model indicated that cations with stronger hydration energy introduce a higher number of co-intercalated water molecules into the channel, consistent with early experimental observation obtained for MXene (2D transition metal carbide) channels. The predicted optimal water numbers for the cations were then used for AIMD simulations that explicitly include the effects of the solvent. When compared with the cations in bulk solution, our simulations showed that the hydration structure and coordination number (CN) of the solvated cations confined in the MoS₂ channel can be significantly altered. Further, we found that larger cations with weaker hydration energy (K⁺, Rb⁺, and Cs⁺) exhibited a distinctive CN decrease under confinement, while smaller cations (Li⁺ and Na⁺) retained a similar hydration shell as in the bulk solution. More specifically, the hydration shell of large cationsmore » (K⁺, Rb⁺, and Cs⁺) in MoS₂ showed similar features of the coordination angle to the bulk, which suggests the partially broken hydration shell with no geometry change under confinement. Our simulations provided insights into the change of the hydration structure of alkaline metal cations under confinement, which may have important implications on their transport in the 1T-MoS₂ channel.« less

Authors:

Zhan, Cheng  ^[1];

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Sun, Yangyunli ^[2]; Aydin, Fikret ^[1]; Wang, Y. Morris ^[3]; Pham, Tuan Anh ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Univ. of California, Riverside, CA (United States)
3. Univ. of California, Los Angeles, CA (United States)

Publication Date:

Fri Apr 23 00:00:00 EDT 2021

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Enhanced Nanofluidic Transport (CENT)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1781759

Report Number(s):

LLNL-JRNL-818694
Journal ID: ISSN 0021-9606; 1029289; TRN: US2210308

Grant/Contract Number:  

AC52-07NA27344; SC0019112

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 154; Journal Issue: 16; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Reference interaction site model; First-principle calculations; Nanomaterials; Density functional theory; Implicit solvation; Energy storage; Ab-initio molecular dynamics; Nanochannels; Desalination; Porous media