可极化分子模拟揭示含硅官能团如何控制纳米多孔石墨烯中的脱盐机制
Polarizable Molecular Simulations Reveal How Silicon-containing Functional Groups Govern the Desalination Mechanism in Nanoporous Graphene
摘要：
我们报告了分子动力学（MD）模拟研究反渗透脱盐使用纳米多孔单层石墨烯钝化SiH $_2$和Si（OH）$_2$功能团。建立了一个高精度、精细化的可极化分子力学力场模型，用于模拟各种尺寸和几何形状的石墨烯纳米孔。模拟的水通量和离子排斥率的解释使用详细的原子机制来自模拟轨迹的分析。我们的主要发现是：（1）Si（OH）$_2$孔由于Cl $^-$离子的选择性静电排斥而具有优异的离子截留率，但Na $^+$离子被吸引到孔中并阻止水传递。(2)相比之下，SiH $_2$孔通过基于其水合层的尺寸和柔性排除离子的空间机制来操作。(3)在没有离子的情况下，水通量是成正比的孔隙内的溶剂可访问的区域，然而，模拟通量低于从最近的实验工作推断。我们还提出了一些假设，可以解决模拟和实验之间的差异。
英文摘要：
We report a molecular dynamics (MD) simulation study of reverse osmosis desalination using nanoporous monolayer graphene passivated by SiH$_2$ and Si(OH)$_2$ functional groups. A highly accurate and detailed polarizable molecular mechanics force field model was developed for simulating graphene nanopores of various sizes and geometries. The simulated water fluxes and ion rejection percentages are explained using detailed atomistic mechanisms derived from analysis of the simulation trajectories. Our main findings are: (1) The Si(OH)$_2$ pores possess superior ion rejection rates due to selective electrostatic repulsion of Cl$^-$ ions, but Na$^+$ ions are attracted to the pore and block water transfer. (2) By contrast, the SiH$_2$ pores operate via a steric mechanism that excludes ions based on the size and flexibility of their hydration layers. (3) In absence of ions, water flux is directly proportional to the solvent accessible area within the pore; however, simulated fluxes are lower than those inferred from recent experimental work. We also provide some hypotheses that could resolve the differences between simulation and experiment.
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