RII Track-4: Electrochemical Modulation of Permeability and Selectivity of Conductive MXene Membranes

开发高效的膜基海水淡化和净化技术对于解决水资源短缺和污染的全球挑战至关重要。理想的分离膜应具有高透性（所需物质的输送）和高选择性（不需要物质的排斥），这两个特性通常是负相关的。在诸如海水淡化和去除水中重金属的过程中，带电离子通过尺寸排斥或与膜的静电相互作用从水中分离出来。二维（2D）材料是由一层或几层原子组成的晶体材料，近年来在制造高效膜方面引起了人们的极大兴趣。与现有的膜相比，基于二维材料的纳米多孔膜或层状膜可能以更高的速率和更有效地从水中分离离子。本项目的主要目标是了解应用电化学电位对基于二维过渡金属碳化物（MXenes）的导电膜分离性能的影响。为了实现这一目标，PI将与东北大学的研究人员合作，制造纳米多孔和层状MXene膜，并研究它们的分离性能。此外，该项目将为培养先进膜材料合成和表征方法的研究生提供机会，并将建立奥本大学和东北大学之间的长期合作关系。PI还将把这项研究的结果整合到最近开发的一门专注于二维材料应用的课程中。与现有膜相比，基于2D MXenes的电活性膜可以以更高的速率和效率从水中分离金属离子和其他带电物质。该项目将为基于导电二维MXenes的电活性纳米孔膜和层状膜的设计提供科学框架。将合成两种不同MXenes （Ti3C2和Ti2C）的单层薄片，并将其用于制备膜。本项目中使用的实验测量装置和程序将能够精确测量膜特性，以了解应用电化学电位对制备膜的渗透性和选择性的影响。我们假设，通过外部电化学电位增强MXene膜的电荷排斥机制，可以设计出具有更大纳米通道或纳米孔但具有相似或更好的排斥性能的膜。研究小组将研究应用电位的大小和符号对膜对水中各种阳离子和阴离子的选择性的影响。虽然这个项目特别关注MXenes作为膜材料，但它的研究计划解决了关于离子和带电膜相互作用的基本问题，并且提议的研究结果可能适用于使用其他二维材料制造的膜。研究结果和结论将通过出版物和简报向科学界和公众传播。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The development of efficient membrane-based water desalination and purification technologies is essential for addressing the global challenges of water scarcity and pollution. An ideal separation membrane should show high permeance (transport of desired species) and high selectivity (rejection of undesired species), two properties that are often inversely correlated. In processes such as water desalination and removal of heavy metals from water, charged ions are separated from water by size exclusion or electrostatic interactions with a membrane. Two-dimensional (2D) materials are crystalline materials consisting of one or few layers of atoms and have attracted much interest in recent years for the fabrication of efficient membranes. Nanoporous or lamellar membranes based on 2D materials can potentially separate ionic species from water at higher rates and more efficiently compared to current membranes. The main goal of this project is to understand the effects of applied electrochemical potential on the separation performance of conductive membranes based on 2D transition metal carbides (MXenes). To achieve this goal, the PI will partner with researchers at Northeastern University to fabricate nanoporous and lamellar MXene membranes and study their separation properties. In addition, this project will provide opportunities to train graduate students in advanced membrane materials synthesis and characterization methods and will establish a long-term collaboration between Auburn University and Northeastern University. The PI will also integrate the result of this research into a recently developed course focused on applications of 2D materials. Electroactive membranes based on 2D MXenes can potentially separate metal ions and other charged species from water at higher rates and efficiencies compared to current membranes. This project will provide a scientific framework for designing electroactive nanoporous and lamellar membranes based on conductive 2D MXenes. Single-layer flakes of two different MXenes, Ti3C2 and Ti2C, will be synthesized and used for the fabrication of the membranes. Experimental measurement setups and procedures used in this project will enable accurate measurements of membrane properties to understand the effects of applied electrochemical potentials on the permeability and selectivity of the fabricated membranes. We hypothesize that by enhancing the charge exclusion mechanism of MXene membranes through an external electrochemical potential, membranes with larger nanochannels or nanopores but similar or better rejection properties can be designed. The research team will investigate the influence of the magnitude and sign of the applied potential on the selectivity of membranes towards various cations and anions in water. While this project is specifically focused on MXenes as membrane materials, its research plan addresses fundamental questions about the interactions of ions and charged membranes, and the results of the proposed research may apply to membranes fabricated using other 2D materials. The research results and conclusions will be disseminated through publications and presentations to both scientific and public audiences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.