海水淡化用碳基电极材料及电容去离子技术研究进展

电容去离子技术(Capacitive Deionization,CDI)可以通过断电或电极反接方式使盐离子脱附,达到电极再生的目的,实现电极的可循环利用,其在海水淡化处理技术中具有独特的优势,逐渐成为一种缓和淡水资源紧缺和水污染的极具前景的技术手段。近年来,CDI处理技术正在向电极高效、无二次污染方向转变,未来将进一步聚焦碳基电极材料功能化(碳材料,钛碳化物MXenes,掺杂改性石墨烯材料)、装置和工艺设计优化等重要方向。为深入研究CDI海水淡化技术机理,进一步探索CDI方法在实际应用中的潜力,分别对CDI的脱盐机理、电极材料、装置和工艺设计对电吸附效率和性能的研究进展进行了总结,回顾CDI脱盐效果与电极材料、CDI电池装置设计等因素之间的密切关系,并对CDI技术在海水淡化中的研究发展提出展望。     

电容去离子除氯电极的构建及其脱盐性能研究进展

电容去离子技术(Capacitive deionization,CDI)是一种新兴的脱盐技术,通过在电极两端施加较低的外加电场除去水中的带电离子和分子,由于其较低的能耗和可持续性而备受关注。基于储能电池领域近年来的迅猛发展,CDI电极材料实现了从以双电层作用机理为代表的碳材料到法拉第电极材料的跨越,使得脱盐性能有了大幅度提升。Na⁺的去除与Cl^-的去除同等重要,然而,CDI中针对氯离子高效去除的电极材料研究关注较少。本文从CDI装置的构型演变发展出发,系统地归纳与梳理了CDI中关于脱氯电极材料的分类,对比了不同类型脱氯电极材料的特点,并总结了Cl^-去除的机理,分别为基于双电层的电吸附、转化反应、离子插层和氧化还原反应。本文是首篇关于CDI阳极材料的进展综述和展望,为CDI除氯电极的后续研究提供理论基础和研究思路。     

电容去离子脱盐装置构型的研究进展

电容去离子(CDI)技术是一种新型的海水淡化技术,因其具有环境友好、操作简单和能耗低等优势而受到广大研究者的关注。在CDI技术中,电吸附的性能与装置的构型有着密切的联系。本文综述了目前常见的几种CDI装置,包括膜电容去离子(MCDI)、流动电极电容去离子(FCDI)、杂化电极电容去离子(HCDI)、反式电极电容去离子(i-CDI)以及脱盐电池(DB),对这几种装置的发展历程和装置构型进行介绍,最后,对CDI的装置构型在未来的研究发展方向进行了展望,以期为CDI装置在电脱盐领域的研究和应用提供参考。     

石墨烯基电极材料的设计和构建及其在电容去离子中的应用

电容去离子(CDI)是一种通过静电力作用将离子从水中去除的技术,电极是整个装置中为最为核心的部件,石墨烯因具有优异的导电性和巨大的比表面积等优势成为当前CDI电极材料的研究热点之一。目前对于CDI石墨烯电极的研究主要集中于石墨烯电极的合成,然而有关CDI性能与石墨烯电极制作工艺及电极材料自身结构之间的关系,缺少相关综述。本文系统介绍了CDI的基本原理与性能指标,综述了石墨烯电极材料的研究进展与电极制作工艺,重点分析、归纳和总结了石墨烯材料的特性(孔隙结构、导电性、亲疏水性)对CDI性能的影响,最后对CDI中石墨烯电极材料今后的发展进行了总结和展望。     

电容去离子过渡金属基电极设计及应用研究进展北大核心CSCD

电容去离子(Capacitive deionization,CDI)作为一种新兴的水淡化和离子分离方法,由于其离子选择性高、水回收率高和能耗低等优点受到广泛关注。与传统的基于碳电极的CDI相比,新兴的法拉第电极通过离子捕获的法拉第反应,提供了使得CDI的脱盐性能大幅提升的独特机会。而过渡金属基电极由于其高度可逆的法拉第响应,相对较高的导电性以及出色的理论赝电容值等优势,在CDI电极设计领域受到广泛关注。本文系统地归纳和梳理了过渡金属基电极在CDI应用中的材料分类,总结了针对其本征缺陷所进行改性工程,主要包括导电材料耦合、功能结构工程和缺陷工程等,并对其在海水淡化中的性能进行了总结;此外,从离子选择性分离、金属离子去除和营养元素回收等方面介绍了过渡金属基电极在CDI中的特定应用。最后,概述了剩余的挑战和研究方向,为未来的过渡金属基电极的开发与研究提供指导。     

具有阴阳离子插入行为的电容去离子电极设计

具有离子嵌入/脱嵌能力的离子插层型电容去离子(CDI)电极材料是一类具有很高比容量的新型CDI电极,可以有效改善传统碳材料电极离子存储容量有限、电极易腐蚀的缺点。本文以金属氧化物、过渡金属/碳/氮/碳氮化物(MXenes)、钠超离子导体(NASICON)型磷酸盐材料等为分类,综述了近几年具有代表性的基于离子嵌入/脱嵌的电极材料的设计及在CDI方面的应用,以期深入理解构效关系,开发出性能更强的电极材料。     

一种新型无粘结剂电极的制备及电吸附脱盐性能研究

以椴木为前驱体、二氧化碳为活化剂,制备出具有一定强度、无需粘结剂的电极材料,同时可用作集流体。通过扫描电镜、X射线衍射、拉曼光谱和孔径分析等对材料的形貌和孔结构进行了分析,并使用电吸附脱盐装置测试了其电吸附脱盐性能。结果表明,该材料有大量的微孔结构,比表面积为1440m2/g,其电吸附脱盐能力随着溶液浓度的提高而升高,在溶液浓度为200、500、1000和2000 mg/L时,吸附量分别为2. 02、3. 76、6. 21和12. 42 mg/g。     

有机电极材料过渡态的研究进展

有机电极材料具有理论比容量大、结构可设计性强、加工使用过程环境友好等优点被广泛应用于二次电池的研究中。有机电极材料在氧化还原过程会产生具有不成对电子的自由基中间体,自由基中间体的稳定程度影响电极材料的电化学性能。通过改变材料的结构可以调控自由基中间体的稳定性,从而优化有机电极材料的电化学性能。本文对有机电极材料在电化学过程中产生的自由基中间体进行了分类介绍,阐明了材料结构、自由基中间体稳定性和电化学性能之间的关系。     

光热转换材料及其在脱盐领域的应用

光热脱盐技术在缓解水资源短缺和减少水环境污染等方面具有重要的应用前景,已吸引了各国研究者的广泛关注。光热脱盐主要是利用光热转换材料将吸收的太阳光能直接、高效地转化为热能,以蒸发水分实现含盐水脱盐和水质净化,其效率取决于光热转换材料的性能。本文综述了近年来太阳能光热转换材料如金属基材料、碳基材料、半导体材料、有机聚合物材料、复合光热材料的研究现状及其光热转换机理,并介绍了光热转换材料在脱盐领域的应用进展。基于上述分析,对光热转换材料在未来脱盐领域的研究前景进行了展望,提出应针对光热转换材料的低强度全光谱吸收和高效转化利用、光热稳定性和重复使用性提高,以及光热脱盐系统的热传递损失最小化和热量利用最大化等方面进行深入探析。     

深度脱盐在超纯水制备中的现状及发展趋势

超纯水制备流程一般分为预处理、脱盐、后处理三个阶段,其中脱盐工艺是超纯水制备的核心阶段,脱盐工艺的先进与否对最终的产品水质有着重大影响。该论文综述了纯水的深度脱盐技术,详细介绍了渗透法(RO)、离子交换法、电去离子法(EDI)、电吸附法(EST)等脱盐技术的相关原理及研究进展,并对六种主流脱盐技术的优缺点和适用范围进行了对比评述,在对当前深度脱盐技术在超纯水制备中应用的总结分析的基础上,指出了未来超纯水制备脱盐技术的发展将寄希望于新型脱盐材料的研发和多种脱盐技术联合使用情况下工艺流程的进一步优化。     

Electrode Materials for Desalination of Water via Capacitive Deionization

Recent years have seen the emergence of capacitive deionization (CDI) as a promising desalination technique for converting sea and wastewater into potable water, due to its energy efficiency and eco-friendly nature. However, its low salt removal capacity and parasitic reactions have limited its effectiveness. As a result, the development of porous carbon nanomaterials as electrode materials have been explored, while taking into account of material characteristics such as morphology, wettability, high conductivity, chemical robustness, cyclic stability, specific surface area, and ease of production. To tackle the parasitic reaction issue, membrane capacitive deionization (mCDI) was proposed which utilizes ion-exchange membranes coupled to the electrode. Fabrication techniques along with the experimental parameters used to evaluate the desalination performance of different materials are discussed in this review to provide an overview of improvements made for CDI and mCDI desalination purposes     

Relation between the charge efficiency of activated carbon fiber and its desalination performance

Four types of activated carbon fibers (ACFs) with different specific surface areas (SSA) were used as electrode materials for water desalination using capacitive deionization (CDI). The carbon fibers were characterized by scanning electron microscopy and N(2) adsorption at 77 K, and the CDI process was investigated by studying the salt adsorption, charge transfer, and also the charge efficiency of the electric double layers that are formed within the micropores inside the carbon electrodes. It is found that the physical adsorption capacity of NaCl by the ACFs increases with increasing Brunauer-Emmett-Teller (BET) surface area of the fibers. However, the two ACF materials with the highest BET surface area have the lowest electrosorptive capability. Experiments indicate that the charge efficiency of the double layers is a key property of the ACF-based electrodes because the ACF material which has the maximum charge efficiency also shows the highest salt adsorption capacity for CDI.     

Development of high quality Fe_3O_4/rGO composited electrode for low energy water treatment

Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe_3O_4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe_3O_4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.     

The electrochemistry of activated carbonaceous materials: past, present, and future

Carbonaceous materials are widely used in electrochemistry. All allotropic forms of carbons??graphite, glassy carbon, amorphous carbon, fullerenes, nanotubes, and doped diamond??are used as important electrode materials in all fields of modern electrochemistry. Examples include graphite and amorphous carbons as anode materials in high-energy density rechargeable Li batteries, porous carbon electrodes in sensors and fuel cells, nano-amorphous carbon as a conducting agent in many kinds of composite electrodes (e.g., cathodes based on intercalation inorganic host materials for batteries), glassy carbon and doped diamond as stable robust and high stability electrode materials for all aspects of basic electrochemical studies, and more. Amorphous carbons can be activated to form very high specific surface area (yet stable) electrode materials which can be used for electrostatic energy storage and conversion [electrical double-layer capacitors (EDLC)] and separation techniques based on electro-adsorption, such as water desalination by capacitive de-ionization (CDI). Apart from the many practical aspects of activated carbon electrodes, there are many highly interesting and important basic aspects related to their study, including transport phenomena, molecular sieving behavior, correlation between electrochemical behavior and surface chemistry, and more. In this article, we review several important aspects related to these electrode materials, in a time perspective (past, present, and future), with the emphasis on their importance to EDLC devices and CDI processes.     

Single module flow-electrode capacitive deionization for continuous water desalination

The search for novel desalination technologies has recently led to the introduction of flow-electrodes to capacitive deionization (CDI) processes, named as flow-electrode capacitive deionization (FCDI). Unlike classical CDI, which is a discontinuous or semi-continuous process due to the need for regeneration of the electrodes within the same module, flow-electrodes offer new design opportunities which enable fully continuous desalination processes as well as easily scalable systems. Here, we describe a novel system for the continuous desalination of water based on FCDI using a single flow-electrode and a single module. The flow-electrode is based on activated carbon powder suspended in water. During continuous operation of the system, a desalination rate of a 1 g/L NaCl solution of up to 70% is achieved at water recoveries of up to 80%. Additionally we report very good current efficiencies: in case of 80% water recovery, the current efficiency is 0.93. The single flow-electrode single module process might reduce energy and investment costs and lower the threshold to a large scale implementation.     

Graphene–carbon 2D heterostructures with hierarchically-porous P,N-doped layered architecture for capacitive deionization

Exploring a new-family of carbon-based desalinators to optimize their performances beyond the current commercial benchmark is of significance for the development of practically useful capacitive deionization (CDI) materials. Here, we have fabricated a hierarchically porous N,P-doped carbon–graphene 2D heterostructure (denoted NPC/rGO) by using metal–organic framework (MOF)-nanoparticle-driven assembly on graphene oxide (GO) nanosheets followed by stepwise pyrolysis and phosphorization procedures. The resulting NPC/rGO-based CDI desalinator exhibits ultrahigh deionization performance with a salt adsorption capacity of 39.34 mg g⁻¹ in a 1000 mg L⁻¹ NaCl solution at 1.2 V over 30 min with good cycling stability over 50 cycles. The excellent performance is attributed to the high specific surface area, high conductivity, favorable meso-/microporous structure together with nitrogen and phosphorus heteroatom co-doping, all of which are beneficial for the accommodation of ions and charge transport during the CDI process. More importantly, NPC/rGO exhibits a state-of-the-art CDI performance compared to the commercial benchmark and most of the previously reported carbon materials, highlighting the significance of the MOF nanoparticle-driven assembly strategy and graphene–carbon 2D heterostructures for CDI applications.

MOF nanoparticle-driven assembly on 2D nanosheets produces the graphene–carbon heterostructure with hierarchically-porous P,N-doped layered architecture.