Mechanistic Understanding of Capacitive Deionisation (MU-CDI)

水系统中离子的捕获和管理具有广泛的社会意义。最突出的应用之一是海水淡化，由于人口增长和气候变化对淡水资源造成压力，这项技术正成为一项日益重要的技术。近年来，电容去离子(CDI)作为一种替代反渗透等更常见的海水淡化方法的潜在低能耗方法，受到了越来越多的关注。CDI的工作原理是将盐水溶液通过电化学池，在电化学池中，正负盐离子被固定在相反电荷的多孔碳电极的表面。与其他海水淡化方法相比，CDI的优势之一是，在初始离子捕获步骤之后，可以通过将电极排放到单独的流出物中来再生电极。在这一步骤中，用于离子捕获的部分能量被回收，此外，电极的有效再生减少了污垢。尽管CDI有希望，但它的效率在高盐浓度下会降低。在这方面，它不与其他方法竞争，如反渗透处理海水。近年来，人们进行了大量的研究工作，以扩大CDI有效的浓度范围。大多数研究都集中在材料和电池设计的优化上，并取得了相当大的成功，然而，令人惊讶的是，很少考虑到离子行为或每个电极上发生的基本过程的细节。其中一个主要考虑因素是确保离子电荷由电极捕获的离子存储，而不是与进料电解液中的离子交换(这不会降低盐的浓度)。这项建议旨在建立对CDI的机理的理解，并应用这些知识来控制离子存储机制，以优化盐分去除效率。这将通过使用详细的电化学分析和核磁共振(核磁共振)来实现，核磁共振使我们能够“看到”并计算电极中捕获的离子，并将其与电化学反应和盐分去除效率相关联。我们将研究电极的孔径大小和电解液性质，如浓度和存在的离子的性质，如何影响它们被捕获。然后，这些信息将被用于通知和优化电池设计和操作条件(例如，流速和电池电压)。我们拟议的工作必须是基础性的，关键目的是提高对CDI基础科学的理解，而不是制造原型CDI堆栈。然而，通过与学术和工业合作伙伴的合作，我们的目标是合作并确定可扩展和商业相关的电极材料。

The capture and management of ions in water systems are of widespread importance to society. One of the most prominent applications is water desalination, which is becoming an increasingly important technology due to population growth and climate change putting pressure on freshwater resources. In recent years, capacitive de-ionisation (CDI) has gained increasing attention as a potentially low-energy alternative to more common desalination methods such as reverse osmosis. CDI works by passing a saline solution through an electrochemical cell where the positive and negative salt ions are immobilized on the surfaces of oppositely-charged porous carbon electrodes. One of the advantages of CDI over other desalination methods is that following the initial ion capture step, the electrode can be regenerated by discharging into a separate effluent stock. In this step, some of the energy used for the ion capture is recovered, and furthermore, the efficient regeneration of the electrode reduces fouling. Despite the promise of CDI, its efficiency reduces at high salt concentrations. In this respect, it does not compete with other methods such as reverse osmosis for treatment of seawater. In recent years there have been considerable research efforts to extend the concentration range in which CDI is effective. Most development has focused on optimisation of materials and cell designs with considerable success, yet, surprisingly little consideration has been given to details of the the ion behaviour or the elementary processes taking place at each electrode. One of the primary considerations is to ensure that ionic charge is stored by ions being captured by the electrode, rather than being exchanged with those in the feed electrolyte (which does not reduce the salt concentration). This proposal seeks to develop a mechanistic understanding of CDI and apply this knowledge to control the ion storage mechanism to optimize the salt removal efficiency. This will be done through the use of detailed electrochemical analysis and the use of nuclear magnetic resonance (NMR), which allows us to "see" and count ions that are captured in the electrode, and correlate this with the electrochemical response and salt removal efficiency. We will investigate how the electrode pore size and electrolyte properties, such as concentration and the nature of the ions present, affect how they are captured. This information will then be used to inform and optimise the cell design and operational conditions (e.g., flow rate and cell voltage). Our proposed work is necessarily fundamental in nature with the key aim of improving the understanding of the underlying science of CDI, rather than fabrication of prototype CDI stacks. However, through our collaborations with academic and industrial partners, we aim to work with, and identify, scalable and commercially-relevant electrode materials.