Faradaic Materials Research Articles

Battery-Type Desalination Behavior Confined Within Capsules for Efficient Capacitive Deionization.

Battery-type faradaic materials are considered a class of promising electrodes for capacitive deionization (CDI) due to their superior ability to store ions through redox reactions. However, the desalination potential of such electrode materials has not been fully explored subject to the accessibility, conductivity, stability, etc. Herein, embedded battery material Ag nanoparticles is designed in capsule-structural units composed of graphene and constructed freestanding composite electrodes for CDI. Particularly, these Ag nanoparticles confined in interconnected graphene capsules can be both efficiently accessed by the electrolyte and rationally protected by the capsule networks, significantly unlocking their potential as desalination materials. Impressively, the optimized Ag-involved anodes can achieve an ultrahigh NaCl desalination capacity of ≈360 mg g-1 (≈218 mg g-1 for Cl-) at 1.4 V and exhibit good cycling stability. Moreover, the as-designed anodes also have very competitive desalination capacities for other anions, such as SO2- 4 (≈90 mg g-1) and CrO2- 4 (≈77 mg g-1), suggesting the broad applicability of such Ag-involved electrodes. This work shows that the ingenious introduction of space-confined structures is an effective means of unlocking the desalination potential of Ag-based materials, opening up alternative avenues for the development of other high-performance battery-type desalination electrodes.

On the Challenges to Develop Hybrid Faradaic‐Capacitive Electrodes Incorporating a Sacrificial Salt for Lithium‐ion Capacitors: The Case of Li3V1.95Ni0.05(PO4)3‐AC‐Li2C4O4

AbstractThe low capacity of activated carbon (AC) electrodes remains as one of the major limiting factors for the development of high energy density lithium‐ion capacitors (LICs). Hybridization of capacitive AC electrodes by incorporating faradaic materials into the electrode formulation could be performed to enhance the capacity of the overall device. However, this strategy requires an accurate electrode design to maximize the performance. In this work, Li3V1.95Ni0.05(PO4)3 (LVNP) was selected as faradaic material due to its compatibility with AC, showing high capacity, fast ionic diffusion, and relatively high conductivity. Various formulations and mass loadings have been studied to analyze the impact of incorporating LVNP into the positive electrode on the performance of the hybrid electrode. Moreover, for practical LIC applications, a sacrificial salt ‐dilithium squarate, Li2C4O4‐ was included in the hybrid electrode as a pre‐lithiation additive, developing a ternary electrode. The sacrificial salt oxidized releasing lithium ions, while the electrochemical performance of the hybrid positive electrode remained almost unaltered. Finally, a cycle life test combined with a post‐mortem analysis allows understanding the failure mechanisms of the electrode, suggesting the need of further improvements of the electrolyte and electrode‐electrolyte interface to develop long lifetime hybrid faradaic‐capacitive electrodes based on LVNP‐AC active materials.

Multi-metal-doped transition metal compounds for high-performance asymmetric capacitive deionization

To address the limited ion adsorption capacity of carbon-based capacitive deionization (CDI) which primarily relies on double-layer mechanism, recent efforts have focused on the rational design and development of efficient Faradaic materials for CDI applications. In this study, we synthesized and applied Co- and Mn-doped transition metal compounds (Cu₂O@MCF) as the electrodes for asymmetric CDI using a simple hydrothermal method. The synthesized electrodes were analyzed using various characterization techniques, to confirm the successful doping and structural integrity. Electrochemical performance assessments revealed significant improvements in ion-capture capacity and overall desalination efficiency. Specifically, the optimized asymmetric CDI cell configuration, consisting of Cu₂O@MCF(Cl) as an anode and Cu₂O@MCF(Na) as a cathode, led to a significant increase in salt adsorption capacity (27.42 mg/g) over conventional symmetric carbon electrode (11.22 mg/g), an increase of over 2.4 times. Furthermore, the synthesized electrodes demonstrated effective phosphate ion removal, highlighting their potential applicability in wastewater treatment. The findings suggest that multi-metal doping significantly enhances electrode performance by synergistically combining electric double-layer capacitance and pseudocapacitance effects, due to their unique morphological and electrochemical properties. These results contribute to sustainable water treatment and resource recovery efforts, showcasing the effectiveness of the materials in improving CDI performance and opening new avenues for their application in environmental cleanup and resource management.

DBS−-doped polypyrrole/CNTs with 3D conductive architecture connected with MoS2 as symmetrical electrodes for boosted CDI capability

Molybdenum disulfide (MoS2), as an appealing Faradaic material for efficient capacitive deionization (CDI), is limited by unsatisfactory electrical conductivity, inferior removal rate, and restacking. Herein, we develop a CNT/PPy/MoS2 ternary composite using a robust 3D conductive interconnected structure CNT/PPy, constructed from multi-walled carbon nanotubes (MWCNTs) and polypyrrole (PPy) doped with dodecyl benzene sulfonate (DBS-), as the growing substrate to mitigate the aggregation of MoS2 nanoflakes. In this design, CNT/PPy ameliorates the wettability of the composite, provides convenient movement pathways, a fast charge transport rate, and facilitates ions diffusion process. Moreover, reinforced dispersibility and enlarged interlayer spacing of MoS2 nanoflakes supply sufficient embedded sites for ion uptake and rapid transfer. Meanwhile, tight chemical coupling of Mo-N-C bonds can maintain the structural integrity of the composite electrode. Particularly, the symmetrical electrode configuration was established to address the kinetical unbalance of HCDI system. Consequently, the CNT/PPy/MoS2 displays a large specific capacitance of 160.83 F g−1 at 5 mV s−1, which is nearly 4.33 times that of MoS2 (37.17 F g−1). The optimized CNT/PPy/MoS2 cell achieves a maximum desalination capacity of 24.8 mg g−1, ultra-high deionization rate of 5.24 mg g−1 min−1, and superior capacity retention rate of 92.7% over 25 cycles. In addition, Na+ ions were captured by the joint action of cation-exchange of DBS--doped PPy, electrostatic adsorption of CNTs, and intercalation reaction of MoS2. The proposed composite structural design and electrode configuration should be a potential avenue to realize highly efficient deionization.

Cell voltage control on ion selectivity of carbon nanotube-copper hexacyanoferrate with enhanced electrochemical deionization performance

This study utilizes a simple co-precipitation method to synthesize copper hexacyanoferrate (CuHCF) composites reinforced with carbon nanotubes (CNTs) (denoted as CuHCF@CNTs) serving as superior electrode materials for the electrochemical deionization (ECDI) application, a versatile method for brackish water deionization, water softening, and heavy metal removal. The enhanced performance of CuHCF, one of the Prussian blue analogues (PBAs) with typical Faradaic cation-capturing capability, is attributed to the increased charge transfer and a large surface area provided by multi-wall carbon nanotubes (MWCNTs) for the promoting the utilization of CuHCF units within the composites. The ion selectivity of electrode materials is investigated using both batch and microfluidic reactors, revealing a selectivity sequence of K+ > Ca2+ > Na+ > Mg2+. Additionally, this study introduces a novel approach for controlling the ion selectivity of CuHCF@CNT from the operating voltage. By varying the cell voltage, the selectivity factor, βK/Mg, can be increased from 1.7 at 1.2 V to 4.5 at 0.6 V. Our research offers a new perspective on the ion-capturing selectivity of ECDI systems using Faradaic materials in deionization and ion-concentrating applications.

Engineering Faradaic Electrode Materials for High-Efficiency Water Desalination.

Water desalination technologies play a key role in addressing the global water scarcity crisis and ensuring a sustainable supply of freshwater. In contrast to conventional capacitive deionization, which suffers from limitations such as low desalination capacity, carbon anode oxidation, and co-ion expulsion effects of carbon materials, the emerging faradaic electrochemical deionization (FDI) presents a promising avenue for enhancing water desalination performance. These electrode materials employed faradaic charge-transfer processes for ion removal, achieving higher desalination capacity and energy-efficient desalination for high salinity streams. The past decade has witnessed a surge in the advancement of faradaic electrode materials and considerable efforts have been made to explore optimization strategies for improving their desalination performance. This review summarizes the recent progress on the optimization strategies and underlying mechanisms of faradaic electrode materials in pursuit of high-efficiency water desalination, including phase, doping and vacancy engineering, nanocarbon incorporation, heterostructures construction, interlayer spacing engineering, and morphology engineering. The key points of each strategy in design principle, modification method, structural analysis, and optimization mechanism of faradaic materials are discussed in detail. Finally, this work highlights the remaining challenges of faradaic electrode materials and present perspectives for future research.

(Invited) Lessons in Electrode Architecture for Faradaic Desalination

Potable water is an essential supply for humanitarian missions worldwide, yet delivering pre-purified water to remote locations is challenging, dangerous, and expensive. Therefore, it is desirable to develop and deploy on-site and portable desalination/water-purification equipment that draws on local water sources. Present reverse-osmosis systems effectively desalinate seawater, but are energy and time-intensive, require regular maintenance due to membrane fouling, and suffer from poor scalability. Capacitive deionization (CDI) technology provides energy-efficient desalination of brackish waters, but its use remains limited by low-capacity carbon-only electrodes that rely on double-layer ion storage. Transitioning to electrodes that also incorporate Faradaic ion-capturing materials with substantively higher storage capacity expands the efficacy and applicability of CDI. As one example, NRL-developed porous carbon nanofoam (CNF) architectures infiltrated with electrolessly deposited nanometric MnO2 demonstrate 6-fold increase in sodium-ion adsorption capacity compared to bare-carbon CNFs, while solvothermally deposited BiOCl renders a high-capacity chloride-ion adsorption electrode. The tunability of CNFs as an electrode scaffolding affords the opportunity to balance ion-storage capacity and electrolyte transport for optimized desalination performance. Lessons of electrode architecture extend to NRL silver “sponge” electrodes that provide high capacity for chloride, fast uptake dynamics, and opportunities for various flow configurations. Continued progress in bench-top level flow-cells with high-capacity faradaic materials will demonstrate the promise of this technology en route to development of larger-scale prototype desalination devices.

Efficient lithium extraction using redox-active Prussian blue nanoparticles-anchored activated carbon intercalation electrodes via membrane capacitive deionization

Global demand for lithium (Li) resources has dramatically increased due to the demand for clean energy, especially the large-scale usage of lithium-ion batteries in electric vehicles. Membrane capacitive deionization (MCDI) is an energy and cost-efficient electrochemical technology at the forefront of Li extraction from natural resources such as brine and seawater. In this study, we designed high-performance MCDI electrodes by compositing Li+ intercalation redox-active Prussian blue (PB) nanoparticles with highly conductive porous activated carbon (AC) matrix for the selective extraction of Li+. Herein, we prepared a series of PB-anchored AC composites (AC/PB) containing different percentages (20%, 40%, 60%, and 80%) of PB by weight (AC/PB-20%, AC/PB-40%, AC/PB-60%, and AC/PB-80%, respectively). The AC/PB-20% electrode with uniformly anchored PB nanoparticles over AC matrix enhanced the number of active sites for electrochemical reaction, promoted electron/ion transport paths, and facilitated abundant channels for the reversible insertion/de-insertion of Li+ by PB, which resulted in stronger current response, higher specific capacitance (159 F g−1), and reduced interfacial resistance for the transport of Li+ and electrons. An asymmetric MCDI cell assembled with AC/PB-20% as cathode and AC as anode (AC//AC-PB20%) displayed outstanding Li+ electrosorption capacity of 24.42 mg g−1 and a mean salt removal rate of 2.71 mg g min−1 in 5 mM LiCl aqueous solution at 1.4 V with high cyclic stability. After 50 electrosorption-desorption cycles, 95.11% of the initial electrosorption capacity was retained, reflecting its good electrochemical stability. The described strategy demonstrates the potential benefits of compositing intercalation pseudo capacitive redox material with Faradaic materials for the design of advanced MCDI electrodes for real-life Li+ extraction applications.

Flexible structural construction of the ternary composite Ni,Co-Prussian blue analogue@MXene/polypyrrole for high-capacity capacitive deionization

Prussian blue analogues (PBAs), as the representative of Faradaic materials, has drawn extensive attention in capacitive deionization (CDI) for unique redox activity, open framework structure, and low-cost synthesis. However, the serious aggregation, low conductivity, and easy structural collapse of PBAs nanoparticles limit the practical application in CDI. Herein, the ternary composite Ni,Co-PBA@MXene/PPy is flexibly constructed by integrating the collective advantages of Ni,Co-PBA, MXene, and PPy. In this configuration, MXene not only provides high conductivity but also acts as the good substrate for the in-situ homogeneous growth of Ni,Co-PBA nanoparticles. Furthermore, Ni,Co-PBA nanoparticles could effectively inhibit the self-stacking of MXene and facilitate fast ion intercalation. And the doping of Co in Ni,Co-PBA promotes the redox process by the pseudocapacitive contribution. Meanwhile, PPy contributes to accelerating ions transport rate and promoting the structural stability of MXene and Ni,Co-PBA. Consequently, the hybrid CDI cell AC//Ni,Co-PBA@MXene/PPy delivers prominent desalination performance with the high salt adsorption capacity (38.7 mg g−1), rapid salt adsorption rate (10 mg g−1 min−1), low energy consumption (0.283 kWh kg−1-NaCl), and outstanding cyclic stability. Most importantly, the Ni,Co-PBA@MXene/PPy electrode can reserve favorable structural integrity by the significant shielding effect of PPy to prevent Ni,Co-PBA from collapse and MXene from being oxidized.

Electrocapacitive Deionization: Mechanisms, Electrodes, and Cell Designs

AbstractCapacitive deionization (CDI) is an emerging water desalination technology for removing different ionic species from water, which is based on electric charge compensation by these charged species. CDI is becoming popular because it is more energy‐efficient and cost‐effective than other technologies, such as reverse osmosis and distillation, specifically in dealing with brackish water having low or moderate salt concentrations. Over the past decade, the CDI research field has witnessed significant advances in the used electrode materials, cell architectures, and associated mechanisms for desalination applications. This review article first discusses ion storage/removal mechanisms in carbon and Faradaic materials aided by advanced in situ analysis techniques and computations. It then summarizes research progress toward electrode materials in terms of structure, surface chemistry, and composition. More still, it discusses CDI cell architectures by highlighting their different cell design concepts. Finally, current challenges and future research directions are summarized to provide guidelines for future CDI research.

Poly-p-phenylene as a novel pseudocapacitive anode or cathode material for hybrid capacitive deionization

Hybrid capacitive deionization (HCDI), which consists of one Faradaic and one carbon electrode, has recently developed as a high-efficiency and environmentally friendly water desalination technique. The advancement of HCDI, however, is hampered by a scarcity of high quality Faradaic materials. Here we demonstrated that conducting poly-p-phenylene (PPP) with a coplanar molecular structure of the extended Π-conjugated skeleton can be used as a reversible electrode material to capture either cations (Na+, K+, Ca2+) or anions (Cl−, F−, NO3−, and SO42−) from various salt solutions. This is benefited from its broad potential window and n−/p-doping characteristics. The desalination performance of PPP was evaluated systematically with the constructed HCDI cells in different electrolytes, which can deliver excellent salt adsorption capacity, charge efficiency, and long-term cycling stability. Further, based on complex capacitance analysis, the kinetic features and mechanism for the ion insertion-adsorption processes were further elucidated, which offers both a new perspective for understanding the salt removal performance of PPP and a practical method for investigating other pseudocapacitive intercalation materials.

Soft-hard interface design in super-elastic conductive polymer hydrogel containing Prussian blue analogues to enable highly efficient electrochemical deionization.

The poor cycling stability of faradaic materials owing to volume expansion and stress concentration during faradaic processes limits their use in large-scale electrochemical deionization (ECDI) applications. Herein, we developed a "soft-hard" interface by introducing conducting polymer hydrogels (CPHs), that is, polyvinyl alcohol/polypyrrole (PVA/PPy), to support the uniform distribution of Prussian blue analogues (e.g., copper hexacyanoferrate (CuHCF)). In this design, the soft buffer layer of the hydrogel effectively alleviates the stress concentration of CuHCF during the ion-intercalation process, and the conductive skeleton of the hydrogel provides charge-transfer pathways for the electrochemical process. Notably, the engineered CuHCF@PVA/PPy demonstrates an excellent salt-adsorption capacity of 22.7 mg g-1 at 10 mA g-1, fast salt-removal rate of 1.68 mg g-1 min-1 at 100 mA g-1, and low energy consumption of 0.49 kW h kg-1. More importantly, the material could maintain cycling stability with 90% capacity retention after 100 cycles, which is in good agreement with in situ X-ray diffraction tests and finite element simulations. This study provides a simple strategy to construct three-dimensional conductive polymer hydrogel structures to improve the desalination capacity and cycling stability of faradaic materials with universality and scalability, which promotes the development of high-performance electrodes for ECDI.

Scalable Carbon Nanofoams for Faradaic Desalination of Brackish Water

Water scarcity is becoming an increasing exigent humanitarian crisis which can be ameliorated with development of economical and practical water treatment systems. Present reverse-osmosis systems effectively desalinate seawater, but are energy and time-intensive, require regular maintenance due to membrane fouling, and are less adaptable to small scale uses. In contrast, capacitive deionization (CDI) technology shows promise for scalable, energy-efficient desalination of brackish waters, but its application has been limited by reliance on double-layer capacitance ion storage at carbon-only electrodes. Recent advances in electrochemical desalination have focused on exploiting Faradaic (redox-active) materials to increase ion-storage capacity. We design hybrid capacitive deionization (HCDI) flow-cells utilizing scalable, NRL-pioneered porous carbon nanofoam (CNF) architectures that also incorporate environmentally benign, faradaic active materials. Electrolessly deposited nanometric MnO2 on CNFs supports a 6-fold increase in sodium-ion adsorption capacity compared to bare-carbon CNFs, while solvothermally deposited BiOCl in CNFs renders a reversible, high-capacity chloride-ion adsorption electrode. We systematically explore architectural parameters such as the pore size distribution and electrode thickness of the CNF, and faradaic material loading with respect to their optimization for desalination performance in prototype flow-cells. Additionally, the performance of such electrode architectures may be further improved by constructing graded-pore, multilayer CNFs that optimize and balance ion transport to the electrode interior while maintaining high capacity. Continued progress in bench-top level HCDI flow-cells with faradaic materials will validate the promise of this technology en route to demonstrating larger-scale desalination devices.

Formation of a CoMn-Layered Double Hydroxide/Graphite Supercapacitor by a Single Electrochemical Step.

Hybrid electric storage systems that combine capacitive and faradaic materials need to be well designed to benefit from the advantages of batteries and supercapacitors. The ultimate capacitive material is graphite (GR), yet high capacitance is usually not achieved due to restacking of its sheets. Therefore, an appealing approach to achieve high power and energy systems is to embed a faradaic 2D material in between the graphite sheets. Here, a simple one-step approach was developed, whereby a faradaic material [layered double hydroxide (LDH)] was electrochemically formed inside electrochemically exfoliated graphite. Specifically, GR was exfoliated under negative potentials by CoII and, in the presence of MnII , formed GR-CoMn-LDH, which exhibited a high areal capacitance and energy density. The high areal capacitance was attributed to the exfoliation of the graphite at very negative potentials to form a 3D foam-like structure driven by hydrogen evolution as well as the deposition of CoMn-LDH due to hydroxide ion generation inside the GR sheets. The ratio between the CoII and MnII in the CoMn-LDH was optimized and analyzed, and the electrochemical performance was studied. Analysis of a cross-section of the GR-CoMn-LDH confirmed the deposition of LDH inside the GR layers. The areal capacitance of the electrode was 186 mF cm-2 at a scan rate of 2 mV s-1 . Finally, an asymmetric supercapacitor was assembled with GR-CoMn-LDH and exfoliated graphite as the positive and negative electrodes, respectively, yielding an energy density of 96.1 μWh cm-3 and a power density of 5 mW cm-3 .

Regenerative electrochemical ion pumping cell based on semi-solid electrodes for sustainable Li recovery

Demand of lithium is expected to increase drastically in coming years driven by the market penetration of electric vehicles powered by Li-ion batteries, which will require faster and more efficient Li extraction technologies than conventional ones (evaporation in brines). The Electrochemical Ion Pumping Cell (EIPC) technology based on the use of Faradaic materials is one of the most promising approaches. However, its relatively short lifespan prevents its commercial deployment. Herein, a new EIPC concept based on the use of semi-solid electrodes is proposed for the first time, which takes advantage of the rheological characteristics of semi-solid electrodes that enable simple and cheap regeneration of the Regenerative Electrochemical Ion Pumping Cell (REIPC) systems after reaching its end-of-life. A proof-of-concept for REIPC is accomplished by simple replacement of the semi-solid electrode demonstrating a remarkable electrochemical performance (e.g. 99.87%cycle−1, 99.98%h−1, 3–4 mAh cm−2) along with a competitive ion separation (e.g. 16.2 mgLi·gNiHCF−1, 4 gLi m−2 and 15.6 Wh·mol−1). The use of semi-solid electrode offers other unique features such as a significant cost reduction of 95% for every regeneration regarding conventional EIPC, proving that REIPC concept successfully addresses the issues associated to the sustainability and recyclability of the conventional EIPC's for lithium capturing.

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

Capacitive deionization is an emerging and rapidly developing electrochemical technique for water desalination across the globe with exponential growth in publications. There are various architectures and materials being explored to obtain utmost electrosorption performance. The symmetric architectures consist of the same material on both electrodes, while asymmetric architectures have electrodes loaded with different materials. Asymmetric architectures possess higher electrosorption performance as compared with that of symmetric architectures owing to the inclusion of either faradaic materials, redox-active electrolytes, or ion specific pre-intercalation material. With the materials perspective, faradaic materials have higher electrosorption performance than carbon-based materials owing to the occurrence of faradaic reactions for electrosorption. Moreover, the architecture and material may be tailored in order to obtain desired selectivity of the target component and heavy metal present in feed water. In this review, we describe recent developments in architectures and materials for capacitive deionization and summarize the characteristics and salt removal performances. Further, we discuss recently reported architectures and materials for the removal of heavy metals and radioactive materials. The factors that affect the electrosorption performance including the synthesis procedure for electrode materials, incorporation of additives, operational modes, and organic foulants are further illustrated. This review concludes with several perspectives to provide directions for further development in the subject of capacitive deionization. PRACTITIONER POINTS: Capacitive deionization (CDI) is a rapidly developing electrochemical water desalination technique with exponential growth in publications. Faradaic materials have higher salt removal capacity (SAC) because of reversible redox reactions or ion-intercalation processes. Combination of CDI with other techniques exhibits improved selectivity and removal of heavy metals. Operational parameters and materials properties affect SAC. In future, comprehensive experimentation is needed to have better understanding of the performance of CDI architectures and materials.

Visualizing the landscape and evolution of capacitive deionization by scientometric analysis

Capacitive deionization (CDI) as an emerging desalination technology attracts increasing attention due to its advantages such as low cost, environmental friendliness, simple operation, and large water recovery. This study presents a systematic, objective, and comprehensive review of CDI research via scientometric analysis. The dataset was collected from Web of Science and analysed by software Biblioshiny, VOSviewer and CiteSpace. After analysing a sum of 2270 documents, we identified the most influential journals, countries, institutions, authors, and publications. We also mapped the networks of co-authorship, co-citation, and keywords co-occurrence. Desalination has the largest number of publications in CDI. China is the country with the largest number of publications, and Egypt has the highest level of international collaboration. The keyword and cluster analyses demonstrate the evolution of CDI electrodes from traditional carbon materials through carbon-based nanomaterials to Faradaic materials and the diversification of CDI cell architectures. The timeline visualization displays five popular research topics, including electrode materials, charge efficiency, water salinity, CDI cell architectures, and selective removal. Moreover, we provided several recommendations for future research. This article will give authors an intuitive understanding of the research status, frontier topics, and emerging trends in CDI.

Facile fabrication of flower-like binary metal oxide as a potential electrode material for high-performance hybrid supercapacitors

Developing efficient electrode material with rational design and structure remains a crucial and great challenge for the significant improvement of high-performance hybrid supercapacitors (HSCs). Particularly, the performance of the HSCs can be largely enhanced by designing the battery-type Faradaic material with well-defined morphology and defective engineering. Here, a facile and effective strategy is utilized to develop oxygen-deficient flower-like three-dimensional NiMoO4−δ (Od-NMO) nanomaterial via hydrothermal process and following thermal-treatment under an inert-gas atmosphere. The presence of oxygen deficiency in the Od-NMO is evaluated utilizing various spectroscopy techniques by comparing the pristine NiMoO4 (P-NMO) heat treated under an ambient atmosphere. The electrochemical studies indicate that the oxygen defect sites in the Od-NMO electrode have a considerable role in the betterment of supercapacitive performances. Hence, the Od-NMO electrode provides a large specific capacity of 789 mA h g−1 at 1 A g−1 with an excellent rate capability than the P-NMO (579 mA h g−1). Besides, the fabricated HSC based on Od-NMO flower and activated carbon as the positive and negative electrodes, delivers a specific capacitance as high as 153 F g−1 and accomplishes a large energy density (47.76 W h kg−1) and power density (51.69 kW kg−1) with improved long-term stability.

Electroactive self-polymerized dopamine with improved desalination performance for flow- and fixed- electrodes capacitive deionization

Capacitive deionization (CDI) is an emerging desalination technology with several advantages, including a high energy efficiency and a simple process. In particular, flow electrode CDI (FCDI) shows greatly enhanced salt removal performance by supplying slurry electrodes into a cell, resulting in continuous desalination operation. Along with carbon-based electrodes, Faradaic materials have been widely introduced for FCDI desalination to realize a higher salt removal capacitance. Organic redox-active materials have received significant attention for replacing conventional inorganic electrodes due to their superior characteristics such as cost-effective and eco-friendly properties, light weight, and high theoretical capacity. In this study, dopamine was self-polymerized onto carbon surfaces to provide polydopamine (PDA) grown activated carbons (AC). Strong adhesion property of PDA prevented their dissolution in electrolytes during electrochemical reactions. In addition, it provided a much improved surface wettability and suspension stability. Results showed that the salt adsorption capacity of PDA@AC CDI electrode was significantly enhanced from 6.03 to 10.43 mg/g (a 73% increase). Salt removal rate of an FCDI was also greatly increased from 1.20 to 2.12 mmol/m2s (a 76% increase) for a PDA@AC slurry electrode. The demonstrated approach is expected to open a new door for realizing desalination of a highly saline solution including seawater.

The Surge of Metal-Organic-Framework (MOFs)-Based Electrodes as Key Elements in Electrochemically Driven Processes for the Environment.

Metal–organic-frameworks (MOFs) are emerging materials used in the environmental electrochemistry community for Faradaic and non-Faradaic water remediation technologies. It has been concluded that MOF-based materials show improvement in performance compared to traditional (non-)faradaic materials. In particular, this review outlines MOF synthesis and their application in the fields of electron- and photoelectron-Fenton degradation reactions, photoelectrocatalytic degradations, and capacitive deionization physical separations. This work overviews the main electrode materials used for the different environmental remediation processes, discusses the main performance enhancements achieved via the utilization of MOFs compared to traditional materials, and provides perspective and insights for the further development of the utilization of MOF-derived materials in electrified water treatment.