Chen Luohao, Guo Yanan, Xu Zhijun, Yang Xiaoning
State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemical Engineering, Nanjing Tech University, Nanjing, 210009, China.
Chemphyschem. 2018 Nov 5;19(21):2954-2960. doi: 10.1002/cphc.201800428. Epub 2018 Aug 24.
The adsorption of ions on a graphene surface is very important to control relevant graphene-based processes. In this work, a multiscale simulation was carried out to study the adsorption of Na /Cl ions on graphene by combining quantum mechanics calculations and molecular dynamics (MD) simulations. The interaction energies of the ions with graphene were computed using density functional theory (DFT). It was found that the ions show strong interaction with a graphene cluster and the overwhelming portion of the interaction energy is the ion-π orbital interaction. The large orbital interaction can be ascribed to the two contributions arising from the ion-induced polarization of graphene and the charge transfer between ion and graphene. Their different contribution degrees reveal that the polarization effect plays a main role on the orbital interaction for ion adsorption. Comparatively, for Na/Cl atom adsorption, the charge transfer shows large part to the orbital interaction with weak atom-induced polarization. The obtained interaction energies were applied to develop new interaction potentials between ion and graphene, and then MD simulations were used to study the interfacial adsorption behavior of Na /Cl aqueous solution onto the graphene surface. Due to enhanced ion-π interactions, Na /Cl cooperatively demonstrates a strong ion adsorption layer through direct contact with the hydrophobic graphene surface. Our simulation result presents a new understanding of ion-graphene interactions.
离子在石墨烯表面的吸附对于控制相关的基于石墨烯的过程非常重要。在这项工作中，通过结合量子力学计算和分子动力学（MD）模拟，进行了多尺度模拟来研究Na⁺/Cl⁻离子在石墨烯上的吸附。使用密度泛函理论（DFT）计算离子与石墨烯的相互作用能。发现离子与石墨烯团簇表现出强烈的相互作用，并且相互作用能的绝大部分是离子-π轨道相互作用。大的轨道相互作用可归因于石墨烯的离子诱导极化和离子与石墨烯之间的电荷转移产生的两种贡献。它们不同的贡献程度表明极化效应在离子吸附的轨道相互作用中起主要作用。相比之下，对于Na/Cl原子吸附，电荷转移在与弱原子诱导极化的轨道相互作用中占很大部分。将获得的相互作用能应用于开发离子与石墨烯之间的新相互作用势，然后使用MD模拟研究Na⁺/Cl⁻水溶液在石墨烯表面的界面吸附行为。由于增强的离子-π相互作用，Na⁺/Cl⁻通过与疏水的石墨烯表面直接接触协同形成强离子吸附层。我们的模拟结果对离子-石墨烯相互作用提出了新的理解。
