Recent Advances in Faradic Electrochemical Deionization: System Architectures versus Electrode Materials

Abstract

Capacitive deionization (CDI) is an energy-efficient desalination technique. However, the maximum desalination capacity of conventional carbon-based CDI systems is approximately 20 mg g–1, which is too low for practical applications. Therefore, the focus of research on CDI has shifted to the development of faradic electrochemical deionization systems using electrodes based on faradic materials which have a significantly higher ion-storage capacity than carbon-based electrodes. In addition to the common symmetrical CDI system, there has also been extensive research on innovative systems to maximize the performance of faradic electrode materials. Research has focused primarily on faradic reactions and faradic electrode materials. However, the correlation between faradic electrode materials and the various electrochemical deionization system architectures, i.e., hybrid capacitive deionization, rocking-chair capacitive deionization, and dual-ion intercalation electrochemical desalination, remains relatively unexplored. This has inhibited the design of specific faradic electrode materials based on the characteristics of individual faradic electrochemical desalination systems. In this review, we have characterized faradic electrode materials based on both their material category and the electrochemical desalination system in which they were utilized. We expect that the detailed analysis of the properties, advantages, and challenges of the individual systems will establish a fundamental correlation between CDI systems and electrode materials that will facilitate future developments in this field.

Dimensional optimization enables high-performance capacitive deionization

“…TMO is widely used in energy storage devices for its high conductivity, high reversible Faraday response, abundant natural resources and low manufacturing cost. 153 Chen et al achieved a high specic capacitance of 386 F g À1 at 1 A g À1 based on the structural advantages of 2D-Fe 3 O 4 /C nanosheets, high specic surface area and active sites. 152 With their nanometer/sub-nanometer thickness, almost all metal atoms came in direct contact with the electrolyte and could participate in redox reactions, resulting in pseudocapacitance close to the theoretical value.…”

“…The conductivity of TMD varies according to the arrangement of ions, the structure of the layers and the elements doped. 153 Among them, MoS 2 is a common TMD material. For the rst time, Xing et al used a chemical stripping method to prepare MoS 2 as a CDI electrode material.…”

“…Most inorganic compound CDI electrode materials have problems such as structural damage and material dissolution during the cyclic desalination process, which limit their development. [273][274][275][276][277][278][279] However, due to the diversity of the structure, the versatility of the surface and the good cycle stability, researchers have learned more about polymer-based CDI electrode materials 45,153,[274][275][276][277][278][279] (Fig. 11a and b).…”

Recent progress in materials and architectures for capacitive deionization: A comprehensive review

“…Chen, Sheehan, et al (2020) reviewed various carbon‐based and faradaic materials for heavy metal removal by capacitive deionization, and described the mechanisms of selective heavy metal separations. Recently, Liu, Wang, et al (2021) analyzed properties, advantages, and challenges of various faradaic materials in CDI.…”

Carboxylated graphene oxide nanosheets as efficient electrodes for high-performance supercapacitors

“…Since Becker’s 1957 patent on a carbon electrode supercapacitor with an energy density comparable to batteries and a specific capacitance 3–4 orders of magnitude larger than conventional capacitors ( Lu et al, 2014 ), great deals of efforts have been committed to the exploration and exploitation of carbonaceous resources ( Wang et al, 2017 ; Ren et al, 2022 ). Carbon-based electrodes are notorious with their outstanding thermal-chemical stability, great electrical conductivity, and rich electron density, which allowed their utilization in various applications rooting from catalysis to energy production and conversion technologies ( Bora et al, 2021 ; Eid et al, 2019a ; Eid et al, 2019b ; Eid et al, 2019c ; Eid et al, 2019d ; Xu X. et al, 2020 ; Liu et al, 2021 ; Q. Lu et al, 2021 ; Rasal et al, 2021 ).…”