Faradic Reaction Research Articles

Elucidating the Lithium-Ion Storage Mechanism in Insertion-Available Hard Carbon with Abundant Closed Porosity: Toward a Practical Material for Batteries

In the past two decades, there has been rapid development in high-performance batteries to address the issue of energy shortage. While graphite has served as the negative electrode material for commercial lithium-ion batteries (LIBs), its small theoretical capacity of 372 mAh g−1 and slow kinetics of intercalation/de-intercalation reactions have posed limitations. Thus, there is a quest for alternative materials for further advancement. Hard carbon (HC) has emerged as promising materials for both lithium-ion and sodium-ion batteries (SIBs). HC not only possesses a larger interlayer spacing that facilitates ion diffusion but also features a unique closed pore structure that enables it to achieve a larger theoretical capacity than graphite. These advantages make HC a promising candidate for overcoming the limitations associated with traditional graphite-based electrodes in LIBs. However, recent research has primarily focused on biomass-derived HC and heteroatom-doping HC for LIBs. These HCs, rich in heteroatoms (e.g., N, P, S), often exhibit low initial coulombic efficiencies due to electrolyte consumption of SEI layer which form in the first cycle of lithiation. Additionally, most HC delivers non-faradaic reactions with completely sloping galvanostatic charge-discharge (GCD) curves, indicating pure capacitive responses. This behavior will limit the nominal cell voltage in LIBs. Herein, we propose solutions by introducing phenolic-formaldehyde resin-derived HC microbeads with tunable microporous structures ,aiming to establish them as practical material for the negative electrode in LIBs.The carbon porosity is well manipulated by tailoring chemically cross-linked environments via microwave-induced polymerization of phenolic formaldehyde resin. HC samples, prepared at various calcination temperatures under argon, show increased crystallinity with higher calcination temperatures. On the other hand, the diverse molecular properties of gas molecules enable us to differentiate between various pore structures in HCs. N2 adsorption effectively characterizes open pore structures, while O2 adsorption is suitable for identifying closed pore structures. Additionally, CO2 adsorption is employed to distinguish ultra-micropore structures which are smaller than 0.7 nm. By combining the results of multiple gas adsorption isotherms with in situ X-ray diffraction, a solid correlation between porous properties and electrochemical responses has been successfully established. The results indicate that porosity in HC can change with different calcination temperature. With increasing calcination temperatures, open pores are initially transformed into closed pores, and ultimately, non-porous structure are detected. Furthermore, closed ultra-micropores, which play the same role as the graphitic interlayer spacing in graphite, are termed as “active closed pores”, because they can facilitate the insertion of lithium ions and mitigate substantial initial irreversible capacity by blocking the penetration of solvents. Our proposed equation shows that HC calcinated at 900 degrees (HC-900) exhibits the closed pore volume of 0.336 cm3g−1.The HC-900 with abundant active closed pores can deliver a reversible capacity of 550 mAh g−1 at 50 mA g−1 in operating window of 0.001–1.5 V (vs. Li+/Li), with an ultrahigh low-voltage plateau capacity of 230 mAh g−1 contributed by the faradic reaction of lithium-ion insertion in active closed pores. Unlike some reported methods, such as holding at a constant voltage, charging/discharging at a very small current density, or overcharging to negative voltage regions, the insertion of active closed pores is easily unlocked at a current density of 50 mA g−1. Moreover, the HC-900 also demonstrates excellent rate capability (210 mAh g−1 at 2 A g−1) and cycling stability (90% capacity retention after 200 cycles at 0.1 A g−1 and 86% after 1500 cycles at 1 A g−1), ensuring it as an ideal negative electrode material for LIBs. In summary, we have successfully synthesized and tuned the structure of active closed pore-rich HC. Additionally, we have developed an effective method and equation to evaluate the amount of active closed pores, enabling us to achieve a reversible capacity of 550 mAh g-1 for the negative electrode in LIBs. Figure 1

Hydrothermal Formulation of Dy2MoO6@rGO Nanostructure for Supercapacitors

The exceptional intrinsic conductivity and structural stability of mixed transition metal oxides (MTMOs) make them a significant pseudocapacitive electrode for supercapacitors. However, a major challenge is their inappropriate structures facilitating extended cycling life and rapid Faradic redox reactions. The present research reports the hydrothermal combination of dysprosium molybdate (Dy2MoO6) with reduced graphene oxide (rGO) to advance the specific capacitance (Cs) and rate performance of supercapacitors. While comparing pure Dy2MoO6, the Dy2MoO6@rGO nanocomposite exhibits a higher Cs of 1118 F g−1 at a current density (j) of 1 A g−1 and retention capacitance of 83.7 % after 10,000 successive cycles. The enhanced electrochemical performance of Dy2MoO6@rGO results from its advantageous features, such as high structural stability, greater reactive surface area, favorable ion adoption, and rapid ion/electron transfer rate during the redox phenomenon. Furthermore, the asymmetric supercapacitors (ASCs) employing Dy2MoO6@rGO as the positive and activated carbon (AC) as the negative electrodes presented a Cs of 282 F g−1 at a rate of 1 A g−1. When operated at 1.6 V, the constructed Dy2MoO6@rGO//AC ASC achieves an outstanding energy density (Ed) of 19.2 Wh kg−1 and a power density (Pd) of 272.2 W kg−1. These outstanding findings suggest that the created nanostructures Dy2MoO6@rGO can be used in ultra-performance ASC devices. Moreover, the method simplifies developing efficient energy storage devices using MTMOs by enhancing capacitance and expanding the potential range in an alkaline electrolyte.

Electric Demulsification Membrane Technology for Confined Separation of Oil-Water Emulsions.

Demulsification technology for separation of oil-water (O/W) emulsions, especially those stabilized by surfactants, is urgently needed yet remains highly challenging due to their inherent stability characteristics. Electrocoalescence has emerged as a promising solution owing to its simplicity, efficacy, and versatility, yet hindered by substantial energy consumption (e.g., >50 kWh/m3) along with undesirable Faradic reactions. Herein, we propose an innovative electric demulsification technology that leverages conductive membrane microchannels to confine oil droplets from the oil-water emulsion for achieving high energy-efficient coalescence of oil droplets. The proposed system reduces the required voltage down to 12 V, 2 orders of magnitude lower than that of conventional electrocoalescence systems, while achieving a similar separation efficacy of 91.4 ± 3.0% at a low energy consumption (3 kWh/m3) and an ultrahigh permeability >3000 L/(m2·h·bar). In situ fluorescence microscopy combined with COMSOL simulations provided insight into the fundamental mechanistic steps of an electric demulsification process confined to membrane microchannels: (1) rapid electric-field redistribution of oil droplet surfactant molecules, (2) enhanced collision probability due to confined oil droplet concentration under dielectrophoretic forces, and (3) increased collision efficacy facilitated by the membrane pore structure. This strategy may revolutionize the next generation of demulsification and oil-water separation innovations.

Metal cation and crystal lattice water molecule stabilized highly mesoporous manganese oxide network for excellent durable electrode in sodium-ion storage

Potassium birnessite is a remarkable material with a wider inter-planar spacing, which enables to accommodate more electrolytic ions to improve overall electrochemical performances. In this work, controlled synthesis of K0.46Mn2O4(H2O)1.4 (HKMO) nanosheets were interconnected mesoporous networks uniformly grown on carbon cloth (CC) via a one-step hydrothermal process. Specifically, the HKMO sample synthesized at 100 °C for 12 h (100@HKMO-12 h) exhibited a mesoporous morphology with a large specific surface area. The binder-free 100@HKMO-12 h electrode exhibits a maximum specific capacitance of 255F g−1 (323F cm−3) in 1 M NaClO4/acetonitrile electrolyte over a broad potential range of 3 V. DFT studies demonstrated the interlayer distance increased by the insertion of K+ ions into the MnO2 matrix. Bader charge analysis showed a 12.09 |e| charge difference for K-birnessite in the inter-layer region compared to the normal birnessite, supported the increase of inter-layer region in the MnO2 matrix. Significantly, the increased interlayer the distance, promoted rapid intercalation/deintercalation of Na+ ions and allowed the reversible faradic pseudocapacitance reaction to occur at a wider potential window. Moreover, the symmetric full-cell fabricated utilizing the 100@HKMO-12 h electrodes have a wide voltage of 2 V and the device delivered a maximum specific energy of 43 Wh kg−1 (28 Wh cm−3) at a minimum specific power of 556 W Kg−1 (349 W cm−3). Besides, the device showed an excellent capacitance retention of ∼94 % even after 10,000 continuous charge–discharge cycles at a current of 5 A/g, indicating it is a potential candidate for next-generation sodium energy storage devices.

New Hybrid Materials Based on N-Doping Copolymers of Thiophene Derivatives for Electrochemical Energy Storage

Over the past decade, electroactive conducting polymers (ECPs) are among the most potential pseudocapacitive materials for the electrodes of microsupercapacitors. ECPs exhibit several advantages, such as good conductivity (up to 103 S cm-1), flexibility, high specific capacitance (values ranging from 300 to 800 F.g-1 depending on synthesis and electrochemical performance conditions), relatively cheap and ease of synthesis [4]. Therefore, the electrochemical deposition of ECPs revealed a new strategy to design a great variety of various polymer morphologies as an innovative pseudocapacitive materials. Based on the different storage mechanism, electrochemical supercapacitors can be divided into three types, namely electrochemical double layer capacitors (EDLCs), pseudosupercapacitors and hybrid supercapacitors in which ECPs and other pseudocapacitive materials such as carbon materials, transition metal oxides, nitride complexes allow to store higher amount of capacitance per gram (faradic reactions) than EDLCs (pure capacitive energy storage reaction).In this work, we have elaborated new n-doped conducting polymers Poly[3,6-bis(2-thienyl)pyridazine] and Poly[3,6-bis(2-(3-n-hexylthienyl))pyridazine] by making electropolymerization on Pt disk electrode and 3 nm alumina coated silicon nanowires in acetonitrile organic electrolyte. The comonomers 3,6-bis(thienyl)pyridazine and (3,6-bis(2-(3-nhexylthienyl))pyridazine) have been successively synthesized. The produced polymeric materials Poly[3,6-bis(2-thienyl)pyridazine] and Poly[3,6-bis(2-(3-n-hexylthienyl))pyridazine] during n-doping process on Pt working electrode in acetonitrile solution of TBAPF6 (0.1 M) expose very low potential value of -2.23 V and -2.19 V at current density of -0.25 mA.cm-2 and -0.06 mA.cm-2, respectively. The elctropolymerization of synthesized comonomer 3,6-bis(thienyl)pyridazine has been done on Al2O3@SiNWs and resulted in thin layer of polymer film with micropores. The experimental results are compared to electropolymerization study of thiophene monomer on Pt disk and Al2O3@SiNWs electrodes to highlight the similarities and electrochemical advancements.

Synergistic enhancement of electric double layers and faradaic reactions in capacitive deionization: The role of NTP@C composite

Capacitive Deionization (CDI) has received attention for its energy efficiency and minimal environmental impact, but it faces practical limitations due to the constrained desalination capacity of conventional systems. Our study addresses this challenge by introducing a novel electrode material, NaTi2(PO4)3 (NTP) coated with interconnected mesoporous carbon (NTP@C). This innovative material leverages the synergistic effects of electric double layers and faradic reaction conversion faradic. Unlike traditional carbon coating, our new strategy significantly changes the shape of NTP from coral to ellipse, significantly shortening the diffusion path of sodium ions (Na+), thus accelerating the mass transfer kinetics. Comprehensive morphological, structural, and electrochemical analyses reveal that NTP@C outperforms traditional electrodes in terms of electrochemical stability, ion transmission rates, and desalination capacity. At 1.8 V and 3 g/L NaCl concentration, NTP@C achieves a remarkable salt adsorption capacity of 233.07 mg g−1, with a desalination capacity growth rate of 188 % between 1.4 V and 1.6 V—surpassing the 159 % growth rate of NTP. Additionally, NTP@C exhibits higher cycle performance, maintaining 89.42 % stability over 50 cycles compared to NTP’s 74.39 %. The innovative carbon coating technique prevents NTP particle agglomeration, enhances conductivity, and increases the specific surface area, culminating in a unique interconnected and wrapped carbon structure. This results in an exceptional synergy between the electric double layer and faradic reaction conversion faradic, propelling NTP@C to outstanding desalination performance and cycle stability.

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.

Enhancing the supercapacitive performance of a carbon-based electrode through a balanced strategy for porous structure, graphitization degree and N,B co-doping

Regarding carbon-based electrodes, simultaneously establishing a well-defined meso-porous architecture, introducing abundant hetero-atoms and improving the graphitization degree can effectively enhance their capacitive performance. However, it remains a significant challenge to achieve a good balance between defects and graphitization degree. In this study, the porous structure and composition of carbon materials are co-optimised through a ‘dual-function’ strategy. Briefly, K3Fe(C2O4)3 and H3BO3 were hybridised with a gelatin aqueous solution to form a homogeneous composite hydrogel, followed by lyophilisation and carbonisation. Owing to the dual functionality of raw materials, the graphitization, activation and hetero-atom doping processes can occur simultaneously during a one-step high-temperature treatment. The resultant carbon material exhibits a high graphitization degree (ID/IG = 0.9 ± 0.1), high hetero-atom content (N: 9.0 ± 0.3 at.%, B: 6.9 ± 0.5 at.%) and a large specific area (1754 ± 58 m2/g). The as-prepared electrode demonstrates a superior capacitance of 383 ± 1F g−1 at 1 A/g. Interestingly, the cyclic voltammetry (CV) curves exhibit a distinctive pair of broad redox peaks, which is uncommon in KOH electrolyte. Experiment data and density functional theory (DFT) simulation verify that N-5, B co-doping enhances the activity of the faradic reaction of carbon electrodes in KOH electrolyte. Furthermore, the fabricated Zn-ion hybrid supercapacitor (ZHSC) based on this carbon electrode delivers a high-energy density of 140.7 W h kg−1 at a power density of 840 W kg−1.

Proton-selective coating enables fast-kinetics high-mass-loading cathodes for sustainable zinc batteries

The pressing demand for sustainable energy storage solutions has spurred the burgeoning development of aqueous zinc batteries. However, kinetics-sluggish Zn2+ as the dominant charge carriers in cathodes leads to suboptimal charge-storage capacity and durability of aqueous zinc batteries. Here, we discover that an ultrathin two-dimensional polyimine membrane, featured by dual ion-transport nanochannels and rich proton-conduction groups, facilitates rapid and selective proton passing. Subsequently, a distinctive electrochemistry transition shifting from sluggish Zn2+-dominated to fast-kinetics H+-dominated Faradic reactions is achieved for high-mass-loading cathodes by using the polyimine membrane as an interfacial coating. Notably, the NaV3O8·1.5H2O cathode (10 mg cm−2) with this interfacial coating exhibits an ultrahigh areal capacity of 4.5 mAh cm−2 and a state-of-the-art energy density of 33.8 Wh m−2, along with apparently enhanced cycling stability. Additionally, we showcase the applicability of the interfacial proton-selective coating to different cathodes and aqueous electrolytes, validating its universality for developing reliable aqueous batteries.

Sonochemical synthesis of CoNi layered double hydroxide as a cathode material for assembling high performance hybrid supercapacitor

Fabricating battery-type electrode materials with large specific surface area and mesopores is an efficient method for enhancing the electrochemical performance of supercapacitors. This method may provide more active sites for Faradic reactions and shorten the ion-diffusion paths. In this study, the CoNi layered double hydroxides (LDHs) with the morphology of nanoflowers and nanoflakes were prepared in solutions with pH values of 7.5 (CoNi LDH-7.5) and 8.5 (CoNi LDH-8.5) via a simple sonochemical approach. These CoNi LDHs possessed large specific surface areas and favourable electrochemical properties. The CoNi LDH-7.5 delivered a specific capacity of 740.8C/g at a current density of 1 A/g, surpassing CoNi LDH-8.5 with 668.1C/g. The hybrid supercapacitor (HSC) was assembled with activated carbon as the anode and CoNi LDH as the cathode to assess its practical application potential in the field of electrochemical energy storage. The CoNi LDH-7.5//AC HSC achieved the highest energy density of 35.6 W h kg−1 at a power density of 781.1 W kg−1. In addition, both HSCs exhibited little capacity decay over 5,000 cycles at a high current load of 8 A/g. These electrochemical properties of CoNi LDHs make them promising candidates for battery-type electrode materials. The current sonochemical method is simple and can be applied to the preparation of other LDHs-based electrode materials with favourable electrochemical performance.

Faradic side reactions at Ti3C2Tx-based cathode for ammonium extraction studied in a novel PG-MCDI system

This study addresses the challenge of efficient ammonium recovery from wastewater, a key issue in global nitrogen cycle management. A novel capacitive deionization (CDI) system, which innovatively integrated a gas diffusion membrane and a proton exchange membrane, called PG-MCDI, was firstly reported to realize NH4+ recovery from wastewater. This system was specifically designed to regulate the cathode side reaction, particularly oxygen reduction reaction (ORR), to control the local pH near cathode surface to maintain 8 ∼ 10. The pH change can affect the NH4+/NH3 equilibrium, resulted in a speciation change from NH4+ to NH3·NH3 will thus be extracted from the feed solution through gas diffusion membrane. Further, Ti3C2Tx-based particles were developed with enhanced NH4+ adsorption capacity through graphite C doping and a macroporous structure, alongside proper ORR performance reinforced by redox couple TiX+/Ti4+ to keep high interfacial pH. This dual-functional approach significantly improved the NH4+ removal capacity. The integrated PG-MCDI exhibited excellent NH4+ removal capacity of 278 mg N g−1 and energy consumption of 0.73 kWh kg−1N at 1.5 V, which are superior to other electrochemical systems. The PG-MCDI system assembled with Ti3C2Tx-based cathode can be routinely employed as an effective strategy to address the energy and environmental issues of recovering NH4+ from wastewater.

Modelling and optimization of Li+ extraction from brine with high Mg/Li ratio by electrochemically switched ion exchange considering thermodynamics and dynamics simultaneously

Electrochemically switched ion exchange (ESIX) technology has been proven to be an efficient and environmental-friendly method for extracting Li+ from brine lakes. To deeply understand and mathematically express the underlying physical process of Li+ extraction in ESIX, a model is developed to describe Li+ extraction from brine lakes with a high Mg/Li mass ratio (500:1) by ESIX with an electrode coated with λ-MnO2 film. The kinetics and thermodynamics of the Li+ extraction process is considered simultaneously by coupling the Frumkin-Bulter-Volmer theory modified by electroactive site concentration with a modified Gouy-Chapman-Stern model. The local sensitivity analysis indicates that the performance of ESIX in Li+ adsorption is greatly influenced by cell voltage, film mass, and Stern capacitance of carbon black film, whereas these parameters have little effect on Mg2+ adsorption. The individual parameter analysis elucidates that the mass and Stern capacitance of carbon black film can regulate the potential drop distributions in different regions of ESIX system, resulting in a maximum Li+ extraction efficiency of 90.22 % due to the increased driving force in the faradic reaction and reduced charge transfer resistance. The optimization of combined parameters indicates that the optimum operation can be achieved at the conditions with a cell voltage ranging between 1.0 and 1.2 V, a Stern layer capacitance with electric double layer volume for carbon black film of 5.4 × 107 F/L, and an initial Li+ content of the treatment solution: carbon black film: λ-MnO2 film mass ratio of 0.1 kg: 9 kg: 8 kg.

Tailoring the interior structure of Cu2O Shell-in-Shell nanospheres for high-performance electrocatalytic nitrate-to-ammonia conversion

Electrocatalytic nitrate reduction is one of the most promising technology for removing harmful nitrate from water while simultaneously producing value-added ammonia. Regulating the internal structure of the benchmark electrocatalyst copper can further improve nitrate-to-ammonia conversion performance. Herein, we synthesized a series of hollow multi-shell structured Cu2O nanospheres (NSs) via a multistep Ostwald ripening method, and evaluated their nitrate-to-ammonia conversion performance. Results show that 2-shell Cu2O NSs demonstrated the highest nitrate conversion (98.1 %), ammonia selectivity (80.2 %), ammonia Faradic efficiency (70.3 %) and reaction rate constant (0.03 min−1) for nitrate-to-ammonia conversion. Important influencing factors are also examined including applied potentials and nitrate concentrations. Mechanistic study unravels that the outstanding electrocatalytic performance of 2-shell Cu2O NSs originates from the strongest nitrite adsorption so as to enhance nitrate-to-ammonia conversion. Materials characterizations verify that Cu2O NSs were reduced to metallic copper that severed as the real active site during electrocatalytic nitrate reduction. This work unveils the interior structure-dependent electrocatalytic performance of Cu2O NSs for nitrate-to-ammonia conversion, which offers a practical strategy to design structurally novel heterogeneous catalysts for various applications.

Antimony vanadate spheres: Synthesis, characterizations, and use as positive electrode in asymmetric supercapacitor systems

A straightforward wet chemical technique was employed to design and synthesize microstructured SbVO4, and its structural and surface morphological properties were examined using various analytical techniques. The electrochemical performance of SbVO4 NPs was studied using chronopotentiometry, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrode exhibits a specific capacitance (Csp) of 384 Fg−1 at 5 mVs−1, showcasing rapid Faradic redox reactions and efficient charge transfer even at higher scan rates. The relationship between scan rates, Csp, and current densities reveals promising kinetics, with the Csp increasing as the scan rate decreases. The SbVO4 electrode maintains a high capacitance retention of 91 % after 6000 GCD cycles, highlighting exceptional cycling stability. The SbVO4//AC asymmetric device, constructed to assess practicality, displays distinct CV profiles and remarkable reversibility at various scan rates. The device achieves a Csp of 62 Fg−1 at 1 Ag−1, with 84 % capacitance retention after 5000 GCD cycles. A Ragone plot illustrates the device's energy density of 22.04 Whkg−1 and power density of 793.4 Wkg−1, affirming the effectiveness of SbVO4//AC as a robust electrode material for SCs in practical applications.

Organic Faradaic Desalination Cell Based on Polyimide Symmetric Electrodes

Capacitive deionization (CDI) is an energy-efficient and environmentally friendly deionization technology. However, the maximum desalination capacity of conventional carbon-based CDI systems is in the range of 5–25 mg g-1, which compromises the use of this technology in practical applications [1]. Faradaic deionization (FDI) is a promising electrochemical technique, based on storing the ions within the particles/layers of the electrode materials either by intercalation and/or faradic reactions. By this mechanism, FDI has expanded the deionization values above 50 mg g-1. In the last ten years, research on FDI has primarily focused on battery electrode materials, especially in inorganic intercalation compounds, typically used for energy storage [2]. However, inorganic materials have several drawbacks, such as decomposition and dissolution issues, which affect long-term performance along with safety and sustainability aspects and consequently might limit their practical deployment.As an alternative, we introduce in this work for the first time an all-polymer deionization cell in combination with a rocking-chair desalination (RCD) mechanism with the aim of boosting the deionization performance [3]. A proof-of-concept next generation technology is accomplished by using a redox-active naphthalene-polyimide (poly[N,N′-(ethane-1,2-diyl)-1,4,5,8-naphthalenetetracarboxiimide], named as PNDIE), which is a well conductive and free-standing electrode material, as anode and cathode in a symmetric FDI system. Our approach relies on the synergistic combination of smart redox polymer selection i.e. PNDIE, and the advance configuration of this material into a buckypaper electrode architecture. A detailed electrochemical characterization under various operational conditions in three electrodes standard half-cell and in two electrode coin-cell configurations was performed. The results of those experiments provide critical information to build an all-polymer rocking chair system with practical PNDIE electrodes (92.2 mgPNDIE; 9.6 cm2). This novel FDI lab-cell demonstrated a remarkable desalination capacity (155.4 mg g-1 at 0.01 A g-1) together with a high salt-removal rate and productivity (3.42 mg g-1 min-1 at 0.01 A g-1 and 62 L h-1 m-2, respectively). In addition, long-term stability experiments provided salt adsorption capacity retention values over 95 % after 100 cycles (23 days). Compared to the state-of-the-art deionization technologies (CDI, Hybrid CDI and FDI) the reported technique exhibits superior electrochemical and deionization performance. These results support the idea of using organic materials as a viable alternative for robust and sustainable “water-energy” electrochemical applications.

Nanocomposites of Ni-Co-Mn MOFs and PANI functionalized CNTs-GNPs with excellent electrochemical performance for energy storage applications

Supercapacitors, pivotal for eco-friendly energy solutions, demand efficient Ni-Co-Mn MOF-based electrodes. These electrodes, combining carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and polyaniline (PANI), were created through a facile ultrasonication-assisted solvothermal method, fostering their utility in energy storage systems. Scanning electron microscopy (SEM) reveals a distinctive flower-like morphology that facilitates faradic reactions. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy confirm composition and functional group analysis. Comparative studies demonstrate the superiority of the Ni-Co-Mn/PCG (PANI-CNT-GNP) nanocomposite in charge storage over pristine Ni-Co-Mn MOF. Notably, the Ni-Co-Mn/PCG-40 nanocomposite, with 40 mg of PCGs, exhibited outstanding electrochemical performance, boasting the highest specific capacity (1238C/g @ 2 Ag), minimal internal reversibility, and excellent stability. This enhanced performance is attributed to efficient interconnected pathways and the uniform flower-like structure that aids in both electron and ion transportation. The asymmetric supercapacitor assembled from Ni-Co-Mn/PCG-40 showcased exceptional metrics: 380C/g @ 0.7 Ag specific capacity, a maximum energy density of 90 Wh/kg, a maximum power density of 17,000 W/kg, and 100 % stability over 5000 cycles. This research suggests a promising, cost-effective, and environmentally friendly supercapacitor solution for energy storage applications, addressing both pollution mitigation and energy crisis concerns.

Sulfur vacancies reinforced cobalt molybdenum sulfide nanosheets integrated cathode for high energy density hybrid supercapacitors

Rational design and construction of bimetallic sulfide materials integrated cathode with well-defined hierarchical nanoarchitectures plays a vital role in boosting the electrochemical performance of hybrid supercapacitors (HSCs). Herein, sulfur vacancies reinforced cobalt molybdenum sulfide nanosheets (Vs-CMS) integrated cathodes are prepared by hydrothermal and NaBH4 reduction methods. The introduction of sulfur vacancies in CMS not only contributes to more active sites for faradic redox reactions but also accelerates electron and ion transmission. Benefiting from the synergistic effects of well-defined hierarchical nanoarchitecture and sulfur vacancies, the optimal Vs-CMS integrated cathode delivers a high areal capacity of 0.56 mAh cm−2 at 1 mA cm−2, good rate performance of 0.34 mAh cm−2 at 30 mA cm−2, and excellent cycling stability with 96.7% capacity retention after 10,000 cycles. Furthermore, capacitive-type porous framework activated carbon (PFAC) anodes are used to couple with the optimal Vs-CMS cathodes for assembling HSCs. The as-obtained PFAC anodes possess a high specific capacitance of 112.1 F g− 1 at 0.25 A g− 1, high rate capability of 46.3 F g− 1 at 10 A g− 1, and good cycling stability of 95.5% capacitance retention after 10,000 cycles. The as-assembled HSCs deliver maximum energy density of 73.2 Wh kg−1 and power density of 3014.7 W kg−1, and prominent cyclic stability of 93.3% capacity retention after 10,000 cycles.

A review on Co3O4 nanostructures as the electrodes of supercapacitors

Usage of supercapacitors in energy storage applications has now become a new trend due to their auspicious features. The introduction of pseudocapacitance has increased its weightage to be used in a greater number of practical applications. Electrodes are the major constituents of a supercapacitor, based on which the electrochemical performance of the supercapacitor is decided. Among the varieties of electrode materials available, transition metal oxides are the most suitable ones to fulfill the required criteria. Due to the occurrence of faradic redox reactions on the surface of electrodes, the selection of efficient and favorable electrode material plays a major role. Co3O4 (cobalt (III) oxide) is one of the most desirable electrode materials due to its various peculiar features. This paper reviews briefly several factors of Co3O4 as electrode material in supercapacitor applications. It includes comparative discussions towards different synthesize methodologies and the influence of its dimensional morphology on the electrochemical outputs like specific capacitance, energy density, and power density.

Morphology Evolution of NiFe Layered Double‐Hydroxide Nanoflower Clusters from Nanosheets: Controllable Structure–Performance Relation for Green Energy Storage

NiFe‐layered double hydroxide (NiFe‐LDH) as electrode materials for supercapacitors are successfully prepared by green and one‐step hydrothermal method without template. The controllable structure–performance relation of NiFe‐LDH nanoflower clusters (NCs) for green energy storage is realized by regulating reaction time. The morphology evolution of NiFe‐LDH is elucidated. NiFe‐LDH‐24 h offers a unique NC structure and has specific capacitance of 635.8 F g−1 at 1 A g−1, which is larger than one of the reported pure NiFe‐LDHs so far. The improved electrochemical performance of NiFe‐LDH‐24 h NCs is due to its unique structure and synergistic effect between components that cause the larger specific surface area and more electroactive sites for Faradic reaction. The reaction kinetics reveals the electrochemical energy storage mechanism of the NiFe‐LDH‐24 h NCs. The energy storage is contributed by diffusion and surface capacitance. The electrochemical performance of NiFe‐LDH‐24 h NCs is further modified for the first time by doping F, and the specific capacitance of F‐doped NiFe‐LDH‐24 h NCs (1942 F g−1) is increased by 3 times higher than that of NiFe‐LDH‐24 h NCs. This work provides a more solid theoretical basis for green energy storage through morphology control and doping modification strategies.

Designing V2O5/MXene van der Waals heterostructure for complementary electrochromic dual-ion capacitor

Developing highly efficient electrochromic energy storage device (EESD) is desirable for yielding ample color variation and large electrochemical capacity from the viewpoint of practical energy-saving. However, only a single type of cation or anion traveled back and forth between the cathode and anode in conventional electrochromic devices (ECDs) results in low coloration efficiency and long switching time. Herein, for the first time, we designed a multicolor complementary electrochromic dual-ion capacitor (EDIC) based on ion insertion/extraction and doping/de-doping of the anodic and cathodic electrochromic materials, respectively, to realize the fast faradic reaction and rich color variation. Significantly, the prepared V2O5/MXene van der Waals heterostructure with improved conductivity and more “active” sites favors the charge transfer, effectively improving the switching speed and coloration efficiency. Since the excellent ion matching and synergy effect of Li+ insertion/extraction in V2O5/MXene anode and ClO4- doping/de-doping at PANI/TiO2 cathode, the complementary EDIC exhibits significant color changes, large optical modulation (51%), short switching time (2.4/7.2 s) and high coloration efficiency (111 cm2 C−1), which is much superior to traditional V2O5-based ECDs. We believe that this work provides a general strategy for building a complementary EDIC with excellent electrochromic and energy storage performances.