基于共价接枝反应的二维过渡金属碳化物（MXenes）的表面功能化研究

Two-dimensional materials have emerged as a very hot research topic in recent years, and surface functionalization has been one of the most important research directions in the field of 2D materials. However, since 2D transitional metal carbides (MXenes) were found, the research on surface functionalization is obviously inefficient, and especially recently with more MXenes members discovered and more novel properties presented, there is a pressing need to control the surface properties of MXenes and optimize their performance for wider application by surface functionalization. Due to poor compatibility of as-prepared primary MXenes with oil phase and obvious defects that always co-exist with merits, this project proposed to improve the compatibility of MXenes with different materials system by covalently surface modification for the preparation of high-quality solution-based or matrix-based composites, and to cover the shortages of MXenes’ properties in many applications by hybridizing with other materials relying on surface functionalization. For example, grafting aliphatic chain onto the surface of MXenes can improve the oleophilic properties, and grafting polymer chain onto MXenes can improve their solubility in the similar polymer matrix for enhanced mechanical properties, and grafting polyelectrolyte molecules onto MXenes can improve aqueous solubility and enhance their absorbing performance to heavy metal ions and radiative elements, and the loading of different functional nanoparticles on the surface of MXenes may be beneficial for improving the catalytic ability, energy storage performance, microwave absorbing properties, bactericidal activity, and so on. Therefore, it can be seen that covalently surface functionalization can make full use of the advantages of MXenes themselves and as the carrier and the fillers of composites attributed to its large specific surface area, good conductivity and mechanical strength to obtain stable and reliable hybrid systems, and thus broaden the application area of MXenes. In addition, the effect of different composite modes on the properties of hybrid systems will be clarified by comparing the properties of different composites prepared by different composite modes, such as covalent functionalization and so on, and the optimization mechanism of performance of hybrid systems will be established.

二维材料是当前的研究热点，而表面功能化一直是二维材料研究的一个重要方向。当前对二维过渡金属碳化物的表面功能化研究明显不足，随着该材料家族的壮大和功能优势的逐步显现，通过表面功能化调节材料表面性质优化材料性能拓展材料应用的需求越来越迫切。针对当前二维过渡金属碳化物与油性体系相容性差、许多方面性能不足、应用上常常优缺点并存的现状，本项目提出通过表面共价接枝改性调节二维过渡金属碳化物的表面性能，改善其与不同体系的相容性，并通过共价功能化建立复合体系弥补其性能不足，例如通过接枝长链脂肪分子改善其油溶性，接枝聚电解质改善材料的吸附性，加载无机纳米颗粒优化其催化、储能、吸波等性能，充分发挥二维过渡金属碳化物本身及作为载体、复合物添加剂等的性能优势，拓展其应用范围。本申请也将对包括共价功能化在内的多种复合方式制得的复合体系的性能进行分析比对，研究复合方式对材料性能的影响，并建立复合体系的性能优化机制。

MXene是一种过渡金属碳化物的二维材料，具有优异的导电性、大的比表面积、易于规模化制备、好的水溶液处理性以及其他多样的物化性能（如催化、电磁屏蔽、超导、电化学储能等）等优点，在多个领域展示了良好的应用前景。然而其不佳的有机溶剂相容性、较差的化学稳定性以及与正电性电解质的絮凝作用限制了其在广泛领域的应用，本项目意图通过表面共价接枝改性技术赋予MXene新的表面功能，改善其与有机溶剂及有机基体的相容性，提高其化学稳定性，拓展MXene的使用寿命和应用范围。秉持这一宗旨，本项目主要进行了以下方面的研究：MXene的溶液和熔盐法制备方法优化及表面端基调控；MXene的共价和非共价表面改性及改性后产物的溶液分散性、化学稳定性和电性能调查；MXene高分子复合薄膜的制备及机械和电磁屏蔽性能研究； MXene基复合物的传感性能研究；MXene及改性MXene的电化学性能研究。主要取得了以下成果：进一步优化了MXene的液相合成方法并通过固液相方法相结合的方式实现MXene的快速多元素掺杂；提出了一种基于重氮盐的普适的MXene共价表面改性方法，改善了MXene在有机溶液和有机基体中的分散性，提高了材料的抗氧化能力；制备了MXene基高分子复合物的梯度薄膜材料，极大提升了薄膜对电磁波的屏蔽和吸收能力；制备了基于MXene的三类压力传感器，获得了集好的机械柔韧性、高的检测灵敏度和广的检测范围于一体的器件性能（最低检测限达0.6Pa，最大检测压强可达2MPa以上）；探索了MXene及其改性材料在柔性储能器件中的应用，验证了其作为水系二次电池电极材料的潜力。这些研究结果表明共价和非共价表面改性策略对调节MXene材料的性能，拓展MXene的应用领域具有重要作用，有利于推动MXene向实用化方向发展。