Characterizing Structure-Dependent TiS2/Water Interfaces Using Deep-Neural-Network-Assisted Molecular Dynamics,The Journal of Physical Chemistry C

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Characterizing Structure-Dependent TiS2/Water Interfaces Using Deep-Neural-Network-Assisted Molecular Dynamics
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2023-05-15 , DOI: 10.1021/acs.jpcc.2c08581
Lesheng Li ₁ , Marcos F. Calegari Andrade _{2,

3} , Roberto Car _{2,

4,

5,

6} , Annabella Selloni ₂ , Emily A. Carter _{1,

6,

7,

8}

Affiliation

As a promising layered electrode material, TiS₂-based capacitive deionization (CDI) devices for water desalination have attracted significant attention. However, TiS₂/H₂O interfacial features, potentially important for device optimization, remain unidentified. Using Deep Potential Molecular Dynamics (DPMD), we characterized distinct aqueous interfaces introduced by four TiS₂ terminations expected to be present as water intercalates into TiS₂, namely, Armchair, Zigzag, Zigzag-L, and Zigzag-R. First, we assessed important representative physical properties of the system to validate the deep potentials (DPs). DPMD simulations agree well with experiments and first-principles simulations, suggesting the DPs are accurate and reliable. Subsequent simulations of these TiS₂/water interfaces revealed how TiS₂ surface termination influences the structure of interfacial water. This effect is most evident in the first and second water layers close to the TiS₂ surface, and more pronounced when spontaneous dissociative adsorption of water occurs. The extent of water dissociation on each surface was evaluated using enhanced sampling. Zigzag-L is the only interface where proton transfer from adsorbed water to TiS₂ surface S atoms is thermodynamically and kinetically favored. The coexistence of surface four-fold-coordinated Ti (Ti_4c) and one-fold-coordinated S (S_1c) is found to be essential to making proton transfer feasible on the Zigzag-L surface. Furthermore, remaining unprotonated S_1c atoms can act as good proton acceptors after water dissociation. Thus, TiS₂ with Zigzag-L termination may be a surface to avoid in CDI device construction, given that pH fluctuations adversely affect performance. This work provides new understanding of TiS₂/H₂O interfacial features that could aid future design and optimization of TiS₂-based CDI devices for water desalination.

中文翻译：

使用深度神经网络辅助分子动力学表征结构相关的 TiS2/水界面

作为一种很有前途的层状电极材料，基于 TiS ₂的电容去离子 (CDI) 装置用于海水淡化引起了极大的关注。然而，对于器件优化可能很重要的TiS ₂ /H _{2 O 界面特征仍未确定。}_{使用深势分子动力学 (DPMD)，我们表征了由四个 TiS 2}终端引入的不同水界面，这些界面预计会在水嵌入 TiS ₂时出现，即 Armchair、Zigzag、Zigzag-L 和 Zigzag-R。首先，我们评估了系统的重要代表性物理特性以验证深潜势 (DP)。DPMD 模拟与实验和第一性原理模拟非常吻合，表明 DP 是准确可靠的。这些 TiS ₂ /水界面的后续模拟揭示了 TiS ₂表面终止如何影响界面水的结构。这种效应在靠近 TiS2 的第一层和第二层水层中最为_明显表面，并且当水的自发解离吸附发生时更明显。使用增强采样评估每个表面上的水离解程度。Zigzag-L 是唯一在热力学和动力学上有利于质子从吸附水转移到 TiS _{2表面 S 原子的界面。}发现表面四重配位 Ti (Ti _4c ) 和一重配位 S (S _1c ) 的共存对于使 Zigzag-L 表面上的质子转移可行至关重要。此外，剩余的未质子化的 S _1c原子在水离解后可以充当良好的质子受体。因此，TiS ₂考虑到 pH 值波动会对性能产生不利影响，具有 Zigzag-L 终端的表面可能是 CDI 设备构造中要避免的表面。这项工作提供了对 TiS ₂ /H ₂ O 界面特征的新认识，有助于未来设计和优化用于海水淡化的基于TiS _{2的 CDI 设备。}

更新日期：2023-05-15

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