气液介质中氧化石墨烯膜的结构演化与选择性输运行为研究

Graphene oxide membranes have shown excellent molecule and ion filtration properties such as energy-saving, efficient and highly-selective owing to its ultra-thin thickness and rich nanoscale structures. The selective transport properties of the membrane are determined by its microstructure and nano-confined transport efficiency of molecules and ions. However, present experimental results on filtration efficiency and selectivity of graphene oxide membranes are varied due to the complex microstructure and variable configuration evolution coupled with operating conditions, which results in discrepancy on transport pathway and selective mechanism. The research object of this project is investigating the coupling relationship between microstructure of graphene oxide membrane and media properties and establishing an overall transport model of layered graphene oxide membranes by utilizing molecular dynamic simulation combined with theoretical analysis and current experimental results. This project will mainly focus on: (1) the dependency of membrane microstructure evolution on media properties; (2) transport resistance of molecules through the nanostructure of the membrane; (3) characterizing the complex microstructure of graphene oxide membrane by statistical theory and establishing a statistical transport model. Based on these studies, the mechanism of selective transport through complex nano-channels in the membrane will be systematically understood, which can be utilized to design highly efficient and controllable nano-filtration membranes.

氧化石墨烯薄膜因其超薄的厚度和丰富的纳米结构在分子、离子过滤方面表现出节能、高效、选择性高等优异特性。薄膜的选择性输运性质由膜间微结构网络和分子、离子在微结构中的输运性质决定。然而，由于薄膜的微结构及其在介质中的演化规律复杂，目前关于氧化石墨烯膜的筛选过滤效率的各实验结果间差异性较大，膜的输运路径和选择性机制富有争议。本项目以理解介质对氧化石墨烯膜的微结构的调节规律和膜的整体输运模型为研究目标，拟采用分子动力学模拟与理论分析、目前实验结果相结合的方法，主要分为以下三部分进行研究: (1) 薄膜微结构演化与介质物理性质间的耦合规律；(2) 分子在膜间纳米通道中的输运阻值；(3) 根据统计学理论参数化表征膜的复杂微结构并建立统计输运模型。通过以上研究，系统理解膜中复杂纳米通道中的选择性输运机制，用于设计高效、可控的纳滤薄膜。

本项目拟采用分子动力学模拟并结合理论分析和他人实验结果的方法，针对氧化石墨烯膜在不同分子介质中的微结构演化规律以及分子/离子在膜中的输运与分离机制进行研究。具体完成的研究内容分为以下两部分: 1）液体分子在氧化石墨烯膜间纳米通道中的结构演化规律及其对膜微观结构的调节机制。 氧化石墨烯在不同分子蒸汽或者液体介质中，气液分子会对膜的层间距、褶皱等微观结构进行调节。通过对系统分子熵、自由能的计算分析，研究了不同分子在氧化石墨烯膜间刚性/柔性纳米通道的结构演化规律和机制，探讨分子结构演化对通道输运效率的影响。2）分子/离子在氧化石墨烯薄膜层间纳米通道中输运效率及选择特性研究。以石墨烯为代表的二维材料，因其具有原子级厚度、弯曲刚度低，在制备、转移等过程中不可避免得产生褶皱结构，褶皱结构的形成、失稳性质对二维材料及其组装结构的力、热、电、光等性质有显著影响，进而影响其在电子器件、纳滤薄膜等方面的应用。研究了水分子/离子在氧化石墨烯膜间纳米通道中的输运及选择机制。采用弹性理论结合原子模拟定量探讨了氧化石墨烯膜间纳米通道中的柔性褶皱结构的失稳规律并理论预测了其临界失稳条件。结合流固耦合理论分析定量探讨了含褶皱的纳米通道内流致失稳规律，预演展望了其在流动控制、分子/离子选择性输运方面的应用。