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

Salted Dried Bamboo Shoots-Derived Mesoporous Carbon Inherently Doped with SiC and Nitrogen for Capacitive Deionization

Dried bamboo shoots (DBS) are a natural resource with inherent silica content, which can serve as sacrificial templates for the formation of mesoporous carbon but also promote the generation of silicon carbide (SiC). Building on this, we introduced mesoporous and graphitic carbon/SiC (SiC/BSC) as the CDI electrode for copper ion (Cu2+) removal. Mesoporous carbon electrodes facilitate faster ion transport, diffusion, and electron-transfer pathways. Furthermore, SiC accelerates electron transfer and promotes faradic redox reactions during the charge and discharge processes. Consequently, the synergistic effect of SiC/BSC mesoporous carbon material leads to a promising electrode for Cu2+ capacitive deionization. Leveraging these unique properties, the SiC/BSC electrode material exhibits an outstanding CDI performance of 381.5 mg/g at 1.8 V. This study offers a strategy for the preparation of efficient mesoporous carbon materials as CDI electrodes, specifically tailored for the deionization of Cu2+ ions.

Rapid Near-Patient Impedimetric Sensing Platform for Prostate Cancer Diagnosis

With the global escalation of concerns surrounding prostate cancer (PCa) diagnosis, reliance on the serologic prostate-specific antigen (PSA) test remains the primary approach. However, the imperative for early PCa diagnosis necessitates more effective, accurate, and rapid diagnostic point-of-care (POC) devices to enhance the result reliability and minimize disease-related complications. Among POC approaches, electrochemical biosensors, known for their amenability and miniaturization capabilities, have emerged as promising candidates. In this study, we developed an impedimetric sensing platform to detect urinary zinc (UZn) in both artificial and clinical urine samples. Our approach lies in integrating label-free impedimetric sensing and the introduction of porosity through surface modification techniques. Leveraging a cellulose acetate/reduced graphene oxide composite, our sensor's recognition layer is engineered to exhibit enhanced porosity, critical for improving the sensitivity, capture, and interaction with UZn. The sensitivity is further amplified by incorporating zincon as an external dopant, establishing highly effective recognition sites. Our sensor demonstrates a limit of detection of 7.33 ng/mL in the 0.1-1000 ng/mL dynamic range, which aligns with the reference benchmark samples from clinical biochemistry. Our sensor results are comparable with the results of inductively coupled plasma mass spectrometry (ICP-MS) where a notable correlation of 0.991 is achieved. To validate our sensor in a real-life scenario, tests were performed on human urine samples from patients being investigated for prostate cancer. Testing clinical urine samples using our sensing platform and ICP-MS produced highly comparable results. A linear correlation with R2 = 0.964 with no significant difference between two groups (p-value = 0.936) was found, thus confirming the reliability of our sensing platform.

Solar reduced graphene oxide decorated with manganese dioxide nanostructures for brackish water desalination using asymmetric capacitive deionization

Capacitive deionization (CDI) has emerged as a low-cost, reagent-free technique for the desalination of water. This technique is based on the immobilization of dissolved ions on the electrically charged electrodes, by the electrosorption phenomenon. The electrosorption of dissolved ions by using CDI is limited for feed water having a low concentration of salts. To address this problem, we employ an asymmetric capacitive deionization (Asy-CDI) architecture having solar reduced graphene oxide decorated with manganese dioxide nanostructures (SRGO-MnO2 composite). The Asy-CDI possesses an SRGO-MnO2 composite as the cathode and SRGO as the anode with an anion exchange membrane. The cathode formed from the SRGO-MnO2 composite serves the purpose of immobilization of cations, whereas the anode formed from SRGO is responsible for anion removal. The crystal structure, chemical composition and morphology of the as-synthesized SRGO-MnO2 composite electrode materials are characterized by several techniques, confirming that the surface of SRGO is successfully loaded with α-MnO2 nanostructures. The electrochemical characterization reveals a high specific capacitance of the as-synthesized SRGO-MnO2 composite (419.9 F g-1) at 100 mV s-1. The Asy-CDI provides a higher salt adsorption capacity (40.2 mg g-1) compared to Sy-CDI (28.3 mg g-1) with feed water containing a salt concentration of 2000 mg L-1. These results indicate that the Asy-CDI may be employed as an efficient technique for the desalination of high concentration salt water.

Capacitive deionization system with ultra-high salt adsorption performance: from lab design to agricultural applications

Capacitive deionization is an emerging water desalination technology for industrial applications. Recent advancements in electrode design and system development have led to the reporting of ultra-high salt adsorption performance, benefiting its potential application in agricultural water treatment at a potentially low cost. In this study, we provide a comprehensive summary of the porous electrode design strategy to achieve ultra-high ion adsorption performance, considering factors such as experimental parameters, chemically tuned material properties, redox chemistry and smart nanoarchitecture for future electrode design. Furthermore, we endeavor to establish a correlation between capacitive deionization (CDI) technology and its applicability in the agricultural sector, specifically concentrating on water treatment with an emphasis on undesirable ions associated with salinity, hardness, and heavy metals, to achieve harmless irrigation. Additionally, to ensure the efficient and cost-effective application of CDI systems in agriculture, a thorough overview of the literature on CDI cost analysis is presented. By addressing these aspects, we anticipate that ultra-high salt adsorption CDI systems hold great promise in future agricultural applications.

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.

Recent Progress and Challenges in Faradic Capacitive Desalination: From Mechanism to Performance

Due to substantial consumption and widespread contamination of the available freshwater resources, green, economical, and sustainable water recycling technologies are urgently needed. Recently, Faradic capacitive deionization (CDI), an emerging desalination technology, has shown great desalination potential due to its high salt removal ability, low consumption, and hardly any co-ion exclusion effect. However, the ion removal mechanisms and structure-property relationships of Faradic CDI are still unclear. Therefore, it is necessary to summarize the current research progress and challenges of Faradic CDI. In this review, the recent progress of Faradic CDI from five aspects is systematically reviewed: cell architectures, desalination mechanisms, evaluation indicators, operation modes, and electrode materials. The working mechanisms of Faradic CDI are classified as insertion reaction, conversion reaction, ion-redox species interaction, and ion-redox couple interaction in the electrolytes. The intrinsic and desalination properties of a series of Na+ and Cl- capturing materials are described in detail in terms of design concepts, structural analysis, and synthesis modulation. In addition, the effects of different cell architectures, operation modes, and electrode materials on the desalination performance of Faradic CDI are also investigated. Finally, the work summarizes the challenges remaining in Faradic CDI and provides the prospects and directions for future development.

Selective Ion Removal by Capacitive Deionization (CDI)-Based Technologies

Severe freshwater shortages and global pollution make selective removal of target ions from solutions of great significance for water purification and resource recovery. Capacitive deionization (CDI) removes charged ions and molecules from water by applying a low applied electric field across the electrodes and has received much attention due to its lower energy consumption and sustainability. Its application field has been expanding in the past few years. In this paper, we report an overview of the current status of selective ion removal in CDI. This paper also discusses the prospects of selective CDI, including desalination, water softening, heavy metal removal and recovery, nutrient removal, and other common ion removal techniques. The insights from this review will inform the implementation of CDI technology.