等离子体放电反应机理及等离子体聚合膜成膜机理的同步辐射研究

This proposal aims at resolving the problems associated with plasma polymerized membranes, such as the uncertainty of the mechanisms of plasma discharge reaction and the membrane formation during the plasma discharge, and their relatively low electrochemical performance. Based on our years of experience and achievements obtained in material preparation and characterization using the plasma technology, we will design effective and rational solutions to these problems through executing the following aspects of research in this proposed project: 1) Using synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry techniques to investigate the mechanisms of plasma reaction and membrane formation during the plasma discharge; 2) Using high resolution synchrotron radiation photoelectron spectroscopy combined with high resolution transmission electron microscopy and small angle X-ray scattering (SAXS) to study the formation mechanism and controlling methods of nanosized channels in the composite membranes that can promote ion transport in the plasma polymerized membranes; 3) Synthesizing and optimizing plasma polymerized membranes deposited on the both sides of guanidinium-functionalized holey graphene oxide papers. The main focus of the proposed work is to employ synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry techniques to clarify the mechanisms of plasma reaction and membrane formation during the plasma discharge. On this basis, proton exchange membranes comprising a guanidinium-functionalized holey graphene oxide paper with plasma polymerized polymers on its both sides will be fabricated. The membrane with such a structure is expected to be capable of significantly improving its performance as ion exchange membrane, such as high ion conductivity, low fuel permeability, etc. The project is therefore of great significance for fabrication of ion exchange membranes of high performance and promotion of industrialization of alkaline ion exchange membrane fuel cells.

本课题主要针对等离子体聚合膜制备的反应机理和成膜机理的不确定性及其电化学性能不理想等问题展开研究，结合过去几年项目组利用等离子体技术在材料制备和性能研究中所取得的成绩和积累的经验，提出行之有效和合理的实验解决方案，将进行以下研究内容：1）采用同步辐射真空紫外单光子电离技术结合分子束质谱技术研究等离子体放电的反应机理及等离子体聚合膜的成膜机理。2）利用高分辨同步辐射光电子能谱结合高分辨透射电子显微镜技术及小角X射线散射技术研究离子传输的纳米孔道的形成机制与调控方法；3）表面带孔氧化石墨烯纸复合等离子体聚合离子交换膜的制备和电化学性能优化。本课题的主要目标是利用同步辐射真空紫外单光子电离技术和分子束质谱技术弄清楚等离子体放电的反应机理及等离子体聚合膜的成膜机理。在此基础上，制备出高电导率、高稳定性的等离子体聚合离子交换膜。因此，本项目的实施对促进碱性离子交换膜的产业化具有十分重要的意义。

针对等离子体聚合膜制备的反应机理和成膜机理的不确定性及其电化学性能不理想等问题，我们在本项目中发展了一种合成具有高OH-离子电导率、低甲醇渗透率的碱性阴离子交换膜的新方法，即创造性地采用脉冲放电后辉光等离子体聚合法及对带电粒子的通过具有抑制作用的金属珊网来调控等离子体中活性粒子的化学行为，将等离子体聚合膜沉积在胍碱功能化表面带孔氧化石墨烯纸的正反两面制备出三明治结构的碱性阴离子交换膜，既能解决高机械强度的胍碱功能化氧化石墨烯纸与电极之间接触电阻大、催化剂利用率低等问题，还能解决超薄等离子体聚合膜容易引起电池短路而失效的问题。由于等离子体聚合过程同时存在蚀刻过程，为此我们采用深度氯甲基化的方法来提高等离子体聚合碱性阴离子交换膜中功能基团的含量，同时选择碱性更强的季铵基团如N-甲基咪唑作为铵化试剂来替代毒性强的三甲胺试剂，并延长季铵化时间，使等离子体聚合膜中苄基氯基团得到充分季铵化。为了揭示等离子体放电特性与聚合膜的化学结构之间的内在联系，阐明聚合过程中聚合和蚀刻两者之间的竞争机制，采用在线质谱技术及原位光谱法阐明等离子体放电的反应机理及等离子体聚合膜的成膜机理。利用光电子能谱结合高分辨透射电子显微镜技术及小角X射线散射技术研究了离子传输的纳米孔道的形成机制与调控方法，阐明膜内微相结构的分离，促进离子团簇和离子通道的形成。本研究不仅为碱性阴离子交换膜的合成提供了一条新的技术途径，也对等离子体聚合基本过程的认识有着重要的科学价值。. 本项目按照预定计划顺利开展了工作并取得了非常重要的实验结果和重要成果。项目执行过程已发表学术论文29篇，包括SCI论文28篇，中文核心期刊1篇；发表会议论文3篇；授权国家发明专利4项；培养硕士生2 名，本科生10名。