Superior Electrode Materials Research Articles

Redox-mediated synthesis of Cu2O/CuO/Mn3O4/C quaternary nanocomposites as an efficient electrode material for oxygen reduction reaction and supercapacitor application

Earth-abundant transition metal oxides (TMOs) hold significant promise as electroactive materials in various electrochemical energy conversion and storage applications, offering economic and environmental advantages over their less abundant counterparts. In this work, a simple and cost-effective redox-mediated reaction strategy under hydrothermal conditions has been adopted to synthesize the quaternary nanocomposites Cu2O/CuO/Mn3O4/C with variable amounts of carbon. The synthesized nanocomposites have been characterized using various analysis techniques, including powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET). The synthesized COM5 nanocomposite (Cu2O/CuO/Mn3O4/C-50), when used as an electrocatalyst for the oxygen reduction reaction (ORR), demonstrates a good limiting current density (JL), half-wave potential (E1/2), and onset potential (Eonset) of −5.50 mA/cm2, 0.75 V, and 0.95 V, respectively, as per the polarization curve. The COM5 nanocomposite exhibits a four-electron transfer mechanism, calculated using the Koutecky-Levich (K-L) equation. In an O2-saturated 0.1M KOH solution, the COM5 nanocomposite has shown a superior relative current durability of 84.46% over 14,000 s compared to the commercially available 10 wt% Pt/C, indicating its potential application in the ORR. However, for supercapacitor applications, the COM3 nanocomposite (Cu2O/CuO/Mn3O4/C-20) as active electrode material in galvanic charge-discharge (GCD) study shows superior performance (201 F/g at 1 A/g) compared to the COM2 nanocomposite (117 F/g at 1 A/g) in neutral aqueous electrolyte, possibly due to the lower charge transfer resistance (Rct) of 24.04 Ω compared to COM2 (34.63 Ω). In two-electrode studies, the COM3 nanocomposite exhibits a good energy density of 24.19 Wh/kg at 1 A/g and a 4.7 kW/kg power density at 5 A/g. Additionally, the COM3 nanocomposite shows excellent long-term durability (74% capacitance retention) at the current density of 5 A/g for 8000 cycles. The electrochemical findings indicate that the COM3 nanocomposite stands out as a superior electrode material for supercapacitors, while the COM5 nanocomposite proves to be an effective electrocatalyst for the oxygen reduction reaction.

Copper-Based Electrochemical Sensor Derived from Thiosemicarbazide for Selective Detection of Neurotransmitter Dopamine.

This paper presents the synthesis of the ligand 1-picolinoyl-4-cyclohexyl-3-thiosemicarbazide (H2pctc) and new metal complexes [Ni(Hpctc)2] (1), [Cu(Hpctc)Cl] (2), and [Cd(Hpctc)2] (3). The synthesized metal complexes were precisely characterized using single crystal X-ray diffraction (SC-XRD). In addition, complexes 1-3 were also characterized by UV-vis, fluorescence, and infrared spectroscopy. SC-XRD data confirmed the distorted octahedral geometry around the Ni(II) and Cd(II) centers and the distorted square planar geometry around the Cu(II) center. Data derived from the emission spectra depict that higher fluorescence intensity was exhibited by complexes 1, 2, and 3 in comparison to that of the free ligand H2pctc, and complex 3 showed the maximum intensity. Further, these metal complex-modified GCEs (glassy carbon electrodes) were utilized for electrochemical sensing of dopamine (DPM). The electrochemical studies of these complexes were performed using modified glassy carbon electrodes supported by electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. In contrast to complexes 1 and 3, complex 2 is a superior electrode material with a high effective surface area for the electrochemical oxidation of DPM, according to the electrochemical response results. The derived sensor had a wide linear detection range of 1 to 1400 μM, an acceptable sensitivity of 0.01531 μA cm-2 μM-1, and a low LOD of 0.38 μM. The proposed approach was free of the interfering effects of ascorbic acid, uric acid, aminophenol, and other substances. During the successive scans, no fouling of the electrode surface was observed. The proposed electrochemical sensor had excellent stability, sensitivity, and a low detection limit making it suitable for the analysis of a variety of real samples. Additionally, it was proven to be useful for analyzing biological fluids.

Possible metal oxide cathode materials for Al-ion batteries: A first principle study

This study investigates various Aluminum (Al) -ion oxide cathode materials, considering their structural properties/stability, cell voltage, band gap analysis, and electrical/ion-diffusion rate-capability. The studied materials are AlMn2O4, AlMoO3, AlTiO2, AlV2O5, AlLiCo2O4, and AlCo2O4. The calculations are conducted using Density Functional Theory (DFT) methods, specifically Generalized Gradient Approximation (GGA) and GGA + U. We employ various noble approaches and techniques to assess the properties of the materials. The findings reveal structural stability after deintercalation of Al ion for all the considered structures. AlMn2O4 exhibits the highest stability due to its strong structural framework, while TiO2 is suspected for this property. Voltage estimation suggests higher possible voltages for AlCo2O4 and AlLiCo2O4 materials, despite not being experimentally examined. Calculated intrinsic-like and extrinsic-like band gaps demonstrate the highest conduction for AlCo2O4. Evaluation of rate-capability recognizes the highest electrical/ion-diffusion rate-capability for AlCo2O4 and AlLiCo2O4. Finally, this study introduces two new superior electrode materials for Al-ion batteries (AIBs), i.e. AlLiCo2O4 and AlCo2O4, with promising properties for future AIBs.

Synthesis and electrochemical characterizations of RGO-decorated MnO2 nanorods/carbon cloth-based wearable symmetric supercapacitors

The current research explores a facile two-step method for fabricating flexible RGO-decorated MnO2 nanorod electrodes on a carbon cloth substrate, ideal for wearable energy storage devices. The strategy involves first depositing MnO2 nanorods on the carbon cloth utilizing a hydrothermal technique, followed by a simple ex-situ decoration with reduced graphene oxide by varying concentrations. Through comprehensive physical and electrochemical analyses, the impact of different concentrations of graphene oxide on the physical and electrochemical characteristics of MnO2 electrodes is thoroughly examined. Among the investigated concentrations of graphene oxide, the RGO-decorated MnO2 electrode featuring a 20 mg/100ml concentration of graphene oxide showcased the maximum specific capacitance reaching 1072.28 F/g at a 5 mV/sec in a 1M Na2SO4 electrolyte. Furthermore, this electrode demonstrated commendable long-term cycle stability, preserving over 87% of its original capacitance after enduring 2000 cycles of charge and discharge. A symmetric prototype supercapacitor device has been constructed to assess their practical utility utilizing symmetric electrodes and an aqueous electrolyte. This symmetric device exhibits promising electrochemical properties, underscoring the potential of the developed electrodes for real-world implementation. The remarkable structural, morphological, and electrochemical characteristic attributes of RGO-decorated MnO2 nanorods grown on the carbon cloth substrate position them as superior electrode materials tailored for the burgeoning realm of wearable energy storage devices, paving the way for advanced flexible and efficient energy storage solutions.

Zeolitic imidazolate framework derived stellate shaped cobalt-molybdenum hybrid sulfide microflower for enhanced supercapacitor properties

Zeolitic imidazolate frameworks (ZIFs) represent a class of material exhibiting a well-defined geometry. The ZIF derivatives are known to inherit the parent morphology and have emerged as a potential platform for developing superior electrode materials. In this study, leaf-like ZIF-67 is synthesized using a chemical route and employed as the sacrificial template in one-pot hydrothermal sulfurization for preparing Co3S4-Mo15S19, cobalt‑molybdenum hybrid sulfide (CMS/NF). The unique stellate-shaped architecture of the CMS/NF microflowers enhances the exposure of the redox active sites, improving charge storage and exhibiting superior performance. On account of the synergy of the metal ions and stellate-shaped hierarchical architecture, the CMS/NF hybrid sulfide shows an excellent specific capacitance value of 3283 F g−1 at a current density of 1 A g−1 with capacitance retention of 77.7 % at 10 A g−1. An asymmetric supercapacitor device based on CMS/NF hybrid sulfide with aqueous KOH electrolyte exhibits a high specific energy of 40.8 Wh kg−1 at 400 W kg−1 with excellent cycling life of 81 % after 5000 cycles with ∼100 % coulombic efficiency. In addition, the density functional theory-based simulations have been carried out for the Co3S4-Mo15S19 hybrid system to develop a better understanding. From the total density of states, it is concluded that compared to the pristine structures, the hybrid system has enhanced states close to the Fermi level, confirming the conductivity improvement. Computed quantum capacitance for the pristine and hybrid systems corroborates the experimental capacitance consequences. Hence, the theoretical examinations warrant our electrochemical results and provide insight into developing high-performance supercapacitor electrodes.

Graphene-enhanced manganese dioxide functional ink infused with polyaniline for high-performance screen-printed micro supercapacitor

In the world of miniature advancements in technology, a current champion has emerged: the micro supercapacitors. In order to fabricate these micro-supercapacitors, we have developed a promising and user-friendly approach for printing a conductive functional ink containing a ternary composite of manganese dioxide (MnO2) nanoparticles, Graphene, and polyaniline (PANI) as a dopant. Screen-printing technique was employed to fabricate micro-supercapacitors using the nanocomposite conductive ink. The performance of the energy storage device was examined using flexible symmetric and asymmetric, with an aqueous 1 M KOH electrolyte. According to this strategy, the characterisation and electrochemical study results revealed that doping PANI into both symmetric and asymmetric devices significantly increased the material’s capacitive performance of areal capacitance 167 mFcm−2 for MnO2/Graphene/PANI-5 composite (MGP-5) and 292.5 mFcm−2 for asymmetric supercapacitor (ASSC) at 5 mVs−1. Furthermore, the asymmetric supercapacitor displayed outstanding cyclic stability, retaining 93.6% of its capacitance after 10000 cycles. This underscores the possibility of incorporating polyaniline (PANI) into MnO2 and graphene matrices as efficient blueprints for the development of superior electrode materials. The improvement represents a significant step forward, opening avenues for the future development of novel devices and their integration into top-of-the-line flexible energy storage systems.

Advancing electrochemical activity: Insights from Li doped Ni-MOF synthesis and performance

This study presents the first-time synthesis of a novel Li doped Ni-MOF electrode material, achieved via a one-step hydrothermal strategy. Microstructural analysis using FESEM and HRTEM revealed hierarchical hollow spherical-like nanostructures within the Li doped Ni-MOF, providing abundant active sites for ion transport and storage. This structural feature resulted in enhanced specific capacity, exhibiting battery-like behaviors. Specifically, the Li doped Ni-MOF electrode displayed a notable specific capacity of 214.2 C/g in CV curves at 0.5 mV/s and 814 C/g in GCD curves at 1 A/g. These findings underscore the potential of the Li doped Ni-MOF as a superior electrode material for supercapacitors, indicating its promising prospects for advancing next-generation high-performance energy storage devices.

Flame retardant mechanism-inspired fabrication of all-biomass-derived porous carbons for zinc-ion hybrid supercapacitors

Phosphorus-doped porous carbon materials, sourced from biomass, are becoming increasingly recognized as excellent electrode materials for zinc-ion hybrid supercapacitors (ZHSC). However, existing fabrication methods often involve complexities, a reliance on specialized equipment, and high costs. In this study, we successfully used bamboo fibers and phytic acid to prepare phosphorus-doped porous carbon with a high specific surface area. Our method, which takes advantage of the flame-retardant effect of phytic acid on biomass, eliminates the need for additional water removal steps or pore-forming agents. As such, it offers benefits such as simplicity, cost-effectiveness, environmental sustainability, and adaptability, relying solely on biomass for phosphorus doping and pore formation. The resulting phosphorus-doped porous carbon has a high specific surface area of up to 1229 m2 g−1. Correspondingly, the ZHSC fabricated using this carbon reaches a specific capacity of 109 mAh g−1 in a 2 M ZnSO4 electrolyte. Additionally, a quasi-solid-state flexible ZHSC based on this carbon was successfully manufactured, achieving a maximum energy density of 60 Wh kg−1 and a maximum power density of 1653 W kg−1. These performance metrics surpass those of some similar ZHSCs, underscoring the efficacy of our material fabrication method in producing superior electrode materials for ZHSCs.

Unleashing nature’s energy: Enchanted Albizia amara leaf extract empowers supercapacitors with NdMn2O5 nanocomposite

The potential of using Albizia amara plant extract to synthesize environmentally-friendly Mn3O4, Nd2O3 nanoparticles (NPs) and NdMn2O5 nanocomposites (NCs) for supercapacitor applications was explored. Various techniques will be used to characterize the resulting nanocomposite and evaluate its electrical properties and electrochemical performance. The study will also investigate the impact of synthesis parameters on the nanocomposite properties and optimize them for enhanced supercapacitor performance. Additionally, the environmental sustainability of using Albizia amara plant extract as a green reducing agent will be assessed. The study found that NdMn2O5 nanocomposites possess 754 F/g specific capacitance at 0.5 A/g and concluded superior electrode material properties for supercapacitors compared to the Mn3O4 and Nd2O3 nanoparticles. Moreover, hybrid supercapacitor is employed in as-prepared NdMn2O5 as positive electrode and activated carbon as negative electrode. Assembled hybrid NdMn2O5//AC exhibits 42 Wh/kg specific energy and 379 W/kg power density. 94.34 % of coulombic efficiency and 76.11 % of capacitance retention was perpetuating after 15,000 cycles. The use of Albizia amara plant extract shows promise as green alternative, cost-effective and environmentally-friendly methods for synthesizing NdMn2O5 nanocomposites for energy storage devices.

Dodecyl sulfate ions co-intercalated nickel cobalt carbonate hydroxide with multiwall carbon nanotube: An advanced catalyst for the electrochemical detection of nilutamide

Nilutamide (NLD) serves as a crucial anti-androgen drug for prostate cancer treatment; however, its elevated presence poses ecological risks. Monitoring NLD in environmental and biological samples is imperative. Layered double hydroxide (LDH) stands out as an intriguing electrocatalyst material, and this study focuses on enhancing its properties by hydrothermally preparing a hydrophobic LDH through co-intercalation of dodecyl sulfate anion in nickel cobalt carbonate hydroxide (NCCH). The catalytic performance is further improved by incorporating multiwall carbon nanotubes (MWCNT) to achieve precision and sensitivity in the electrochemical detection of NLD. The resulting NCCH/MWCNT-based electrochemical sensor demonstrates excellent structural, functional, and morphological characteristics verified by various spectroscopic techniques. Electrochemical analyses reveal impressive results, including a low detection limit (0.001 μM), quantification limit (0.0036 μM), two linear ranges (0.01–59.19 μM and 59.19–537.19 μM), and high sensitivity (3.957 μA μM−1cm−2). The practical utility is confirmed through successful monitoring of NLD in environmental and biological samples with satisfactory recoveries. In conclusion, NCCH/MWCNT emerges as a superior electrode material for the selective detection of NLD, showcasing its potential in environmental monitoring and clinical applications.

The Mass-Balancing between Positive and Negative Electrodes for Optimizing Energy Density of Supercapacitors.

Supercapacitors (SCs) are some of the most promising energy storage devices, but their low energy density is one main weakness. Over the decades, superior electrode materials and suitable electrolytes have been widely developed to enhance the energy storage ability of SCs. Particularly, constructing asymmetric supercapacitors (ASCs) can extend their electrochemical stable voltage windows (ESVWs) and thus achieve high energy density. However, only full utilization of the electrochemical stable potential windows (ESPWs) of both positive and negative electrodes can endow the ASC devices with a maximum ESVW by using a suitable mass-ratio between two electrodes (the mass-balancing). Nevertheless, insufficient attention is directed to mass-balancing, and even numerous misunderstandings and misuses have appeared. Therefore, in this Perspective, we focus on the mass-balancing: summarize theoretic basis of the mass-balancing, derive relevant relation equations, analyze and discuss the change trends of the specific capacitance and energy density of ASCs with mass-ratios, and finally recommend some guidelines for the normative implementation of the mass-balancing. Especially, the issues related to pseudocapacitive materials, hybrid devices, and different open circuit potentials (OCPs) of the positive and negative electrodes in the mass-balancing are included and emphasized. These analyses and guidelines can be conducive to understanding and performing mass-balancing for developing high-performance SCs.

Synthesis and characterization of magnesium ferrite-activated carbon composites derived from orange peels for enhanced supercapacitor performance

Supercapacitors have emerged as highly efficient energy storage devices, relying on electrochemical processes. The performance of these devices can be influenced by several factors, with key considerations including the selection of electrode materials and the type of electrolyte utilized. Transition metal oxide electrodes are commonly used in supercapacitors, as they greatly influence the electrochemical performance of these devices. Nonetheless, ferrites' low energy density poses a limitation. Hence, it is crucial to create electrode materials featuring unique and distinct structures, while also exploring the ideal electrolyte types, to enhance the electrochemical performance of supercapacitors incorporating magnesium ferrites (MF). In this study, we effectively prepared magnesium ferrites (MgFe2O4) supported on activated carbon (AC) derived from orange peels (OP) using a simple hydrothermal method. The resulting blends underwent comprehensive characterization employing various methods, including FTIR, XRD, TEM, SEM, EDX, and mapping analysis. Moreover, the electrochemical performance of MgFe2O4@AC composites was evaluated using GCD and CV techniques. Remarkably, the MF45-AC electrode material showed exceptional electrochemical behavior, demonstrating a specific capacitance of 870 F·g−1 within current density of 1.0 A g−1 and potential windows spanning from 0 to 0.5 V. Additionally, the prepared electrodes displayed exceptional cycling stability, with AC, MF, and MF45-AC retaining 89.6%, 94.2%, and 95.1% of their initial specific capacitance, respectively, even after 5000 cycles. These findings underscore the potential of MF-AC composites as superior electrode materials for supercapacitors. The development of such composites, combined with tailored electrolyte concentrations, holds significant promise for advancing the electrochemical performance and energy density of supercapacitor devices.

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.

Interconnected CoNi-Se Hollow Flakes through Reduced Graphene Oxide Sheets as a Cathode Material for Hybrid Supercapacitors.

Achieving a high energy density and long-cycle stability in energy storage devices demands competent electrochemical performance, often contingent on the innovative structural design of materials under investigation. This study explores the potential of transition metal selenide (TMSe), known for its remarkable activity, electronic conductivity, and stability in energy storage and conversion applications. The innovation lies in constructing hollow structures of binary metal selenide (CoNi-Se) at the surface of reduced graphene oxide (rGO) arranged in a three-dimensional (3D) morphology (CoNi-Se/rGO). The 3D interconnected rGO architecture works as a microcurrent collector, while porous CoNi-Se sheets originate the active redox centers. Electrochemical analysis of CoNi-Se/rGO based-electrode reveals a distinct faradic behavior, thereby resulting in a specific capacitance of 2957 F g-1 (1478.5 C g-1), surpassing the bare CoNi-Se with a value of 2149 F g-1 (1074.5 C g-1) at a current density of 1 A g-1. Both materials exhibit exceptional high-rate capabilities, retaining 83% of capacitance at 10 A g-1 compared to 1 A g-1. In a two-electrode coin cell system, the device achieves a high energy density of 73 Wh kg-1 at a power density of 1500 W kg-1, stating an impressive 90.4% capacitance retention even after enduring 20,000 cycles. This study underscores the CoNi-Se/rGO composite's promise as a superior electrode material for high-performance energy storage applications.

Metal-heteroatom-doped CoS/MXene nanohybrid for efficient supercapacitor electrode materials

Developing electrode active materials with abundant active sites, hierarchical porous structure, and good chemical/structure stability significantly promote energy density and cycling stability. However, it is not easy to realize all features for a single component, various strategies such as hetero-atom doping, hybridizing route, and defect engineering could provide possible approaches. Herein, FeCoS were hybridized with MXene to achieve high stability and superior electrochemical performance electrode materials, the well-designed heterogeneous nanohybrids have several merits for abundant active sites, exceptional structural durability, excellent electrical conductivity own to the strong interfacial connection and favorable synergistic effect between the two phases. Consequently, the optimal hybrid electrode demonstrated superior electrochemical performance with an excellent specific capacity of 1190 C g−1 at a current density of 2 A g−1 and outstanding rate capability for 900 C g−1 at 10 A g−1. Moreover, the metal-doped with various cations of Fe2+, Al2+, Ni2+ and Sn2+ were separately introduced into the structural phase to evaluate the feasibility, and the strategy not only provides the feasible and universal development of the stable interface between the hybrids, but also paved the way for the design of high-capacity electrodes.

Synthesis and Optimization of Ni-Based Nano Metal-Organic Frameworks as a Superior Electrode Material for Supercapacitor.

Metal-organic frameworks (MOFs) are hybrid materials that are being explored as active electrode materials in energy storage devices, such as rechargeable batteries and supercapacitors (SCs), due to their high surface area, controllable chemical composition, and periodic ordering. However, the facile and controlled synthesis of a pure MOF phase without impurities or without going through a complicated purification process (that also reduces the yield) are challenges that must be resolved for their potential industrial applications. Moreover, various oxide formations of the Ni during Ni-MOF synthesis also represent an issue that affects the purity and performance. To resolve these issues, we report the controlled synthesis of nickel-based metal-organic frameworks (NiMOFs) by optimizing different growth parameters during hydrothermal synthesis and by utilizing nickel chloride as metal salt and H2bdt as the organic ligand, in a ratio of 1:1 at 150 °C. Furthermore, the synthesis was optimized by introducing a magnetic stirring stage, and the reaction temperature varied across 100, 150, and 200 °C to achieve the optimized growth of the NiMOFs crystal. The rarely used H2bdt ligand for Ni-MOF synthesis and the introduction of the ultrasonication stage before putting it in the furnace led to the formation of a pure phase without impurities and oxide formation. The synthesized materials were further characterized by powder X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), and UV-vis spectroscopy. The SEM images exhibited the formation of nano NiMOFs having a rectangular prism shape. The average size was 126.25 nm, 176.0 nm, and 268.4 nm for the samples (1:1)s synthesized at 100 °C, 150 °C, and 200 °C, respectively. The electrochemical performances were examined in a three-electrode configuration, in a wide potential window from -0.4 V to 0.55 V, and an electrolyte concentration of 2M KOH was maintained for each measurement. The charge-discharge galvanostatic measurement results in specific capacitances of 606.62 F/g, 307.33 F/g, and 287.42 F/g at a current density of 1 A/g for the synthesized materials at 100 °C, 150 °C, and 200 °C, respectively.

Ternary oxides of MnCuNi nanocomposite for enhanced supercapacitor applications

MnO2/CuO/NiO nanocomposites were synthesized at 180 °C via a straightforward hydrothermal approach. The aqueous solutions of Mn, Cu, and Ni salts were combined with KMnO4 to produce these nanomaterials. The same molar ratios were explored to achieve mixed-oxide active materials. The resultant nanocomposites exhibited a phase blend comprising tetragonal -MnO2, monoclinic -CuO, and cubic -NiO. Specifically, the Mn:Cu:Ni nanocomposite with a 1:1:1 ratio showed an impressive specific capacitance of 754.61Fg-1 at a scan rate of 5 mVs−1 and maintained 74 % of its capacity after 5000 cycles, indicating its excellent cyclic stability. This composite electrode surpassed all individual electrodes tested, highlighting its potential as a superior electrode material for supercapacitors. Regarding its performance metrics, the areal capacitance was recorded at 108.79 mFcm−2, while the areal energy and power densities were 0.0283 mWhcm-2 and 0.315 mWcm−2, respectively. These findings signify a significant stride in the development of advanced electrode materials for supercapacitors, suggesting potential applications in other transition-metal-oxide-based electrode innovations.

Tuning the electrochemical performance of Cr2B2 MBene anodes for Li and Na-ion batteries through F and Cl-functionalization: A DFT and AIMD study

In an era in which sustainable energy sources and electric vehicles are prevalent, the development of efficient anode materials is paramount to address the pressing demand for improved energy storage technologies. After the graphene revolution, many other 2D materials such as graphene, MXene (atomically thin layer of Transition Metal Carbide/Nitride/Carbonitride), TMDC (Transition Metal Dichalcogenide), and MBene (atomically thin layer of Transition Metal Borides) have emerged as potential high-performance anode materials. A recent study demonstrated the possibility of synthesizing chromium-based MBenes for the first time, and the electrochemical performance of Cr2B2 as a potential anode material has also been studied theoretically. Inspired by this, the current study utilized density functional theory and ab initio molecular dynamics simulations to probe the role of Cl and F-functionalization of Cr2B2 MBenes as anode materials for rechargeable lithium-ion batteries (LIB) and sodium-ion batteries (NIB). The electronic structure, adsorption, diffusion, and storage capacity of Li (Lithium) and Na (Sodium) were systematically investigated. This study revealed that Cr2B2F2 and Cr2B2Cl2 exhibit excellent conductivity due to their intrinsic metallic properties. In addition, they have low diffusion energy barriers for Li and Na ions (0.13/0.14 and 0.20/0.20 eV for Cr2B2F2 and Cr2B2Cl2, respectively) facilitating rapid charge/discharge rates. The calculations further unveiled a notable Li-ion storage capacity of 818 mAh g-1 for 2D Cr2B2Cl2, accompanied by a moderate open-circuit voltage (OCV) range of 0.38 V to 0.98 V, illustrating its potential as a superior anodic material for LIBs. Similarly, Cr2B2F2 demonstrated a substantial Na-ion storage capacity of 655 mAh g-1, coupled with a reasonably ranged average OCV of 0.20 V to 0.71 V, positioning it as a compelling candidate for NIBs. In all, this investigation has identified two superior electrode materials for alkali-ion batteries, which can spark additional interest in exploring MBene as a promising candidate for advancing next-generation anode materials.

Mns-MWCNT Composite, as a Superior Electrode Material for Asymmetric Flexible Quasi Solid-State Supercapacitors

Nowadays, renewable and sustainable energy sources are being explored and promoted to curb global pollution and to solve the issue of depleting fossil fuel resources. However, these renewable energy sources are intermittent in supply, therefore, it becomes necessary to store them for future usage. The traditional storage devices for electrical energy storage are different kinds of batteries but the sluggish performance of batteries, use of toxic heavy metals, issues pertaining to safety and low cycling efficiency are some of its major drawbacks. Recent proliferation of portable, wearable and flexible electronics and adoption of electric vehicles have forced the scientists to look for fast charging, light weight, leak proof, safe, toxic material free, durable energy storage devices like supercapacitors. Supercapacitors possess fast charge-discharge characteristics, high cycling stability and eco-friendliness in comparison to batteries. But they suffer from extremely low energy density (<10 Wh kg-1), high cost, bulk size, high self-discharge and significant drop in power density while increasing its energy density. The rational synthesis of electrode-materials has a significant impact on the development of high-performance electrodes for energy storage devices. Traditionally semiconducting materials like transition metal oxides are used as pseudocapacitive materials but transition metal oxides have very low electronic and ionic conductivity. Recently, transition metal sulfides, another class of semiconductors, are being investigated as they exhibit better conductivity and reaction kinetics compared to oxides. In this work, α-MnS is selected as an alternative to transition metal oxides. α-MnS is the most stable polymorph among other possible crystal structures of MnS, and has a hexagonal sheet like structure along with high operational potential window than many other metal sulfides. Although it is more conducting than transition metal oxides, it still needs conductivity enhancers like activated carbon, graphene, multiwall carbon nanotubes (MWCNT) etc. External mixing of conductivity enhancers is not effective enough to enhance the conductivity. Hence, MWCNT is mixed during the synthesis step to have a better bonding with α-MnS and create high conductivity channels. α-MnS + MWCNT composite shows a specific capacitance of 115 F g-1 at 1 A g-1 in 3 M KOH electrolyte under 3 electrode configuration. α-MnS + MWCNT composite is deposited on flexible conducting carbon cloth as cathode material and Vulcan carbon is deposited on carbon cloth as anode material. A mixture of poly vinyl alcohol PVA+ 3 M KOH is used as the gel type electrolyte. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic charge discharge (GCD), electrochemical impedance spectroscopy (EIS), cycling stability are performed to characterize the active material and the device performance. The assembled device shows a potential window of 1.4 V, alongside a specific capacitance of 27.7 F g-1 at 1 A g-1 and with 80% of capacity retention after 10,000 cycles. These results prove that transition metal sulfides can be viable alternative materials for supercapacitor application. This quasi-solid state or gel type electrolyte significantly reduces the conductivity and specific capacitance. Enhancing the ionic conductivity of the gel and finding out the optimum thickness of gel electrolyte layer between the electrodes are expected to open new pathways in enhancing the performance of the device. Figure 1

A lamellar chitosan-lignosulfonate/MXene nanocomposite as binder-free electrode for high-performance capacitive deionization

Ti3C2Tx (MXene) is considered as a superior electrode material for capacitive deionization (CDI) due to its high conductivity and two-dimensional structure. However, the electrochemical performance of pristine MXene nanosheets has been significantly impeded by the surface oxidation in the aqueous media and re-stacking caused by van der Waals forces which reduces the ions storage capacity. In this study, the chitosan-lignosulfonate/MXene (CLM) composite was used as a binder-free electrode to enhance the ion storage capacity and long-run cycling stability for hybrid capacitive deionization (HCDI). The chitosan-lignosulfonate nanospheres were able to increase the interlayer spacing between the MXene nanosheets effectively, which has significantly enhanced the ion storage capacity and electrochemical properties of the electrode. The binder-free CLM cathode demonstrated a high salt adsorption capacity of 44.6 mg g−1 and a maximum average salt adsorption rate of 5.8 mg g−1 min−1 at 1.2 V. A high cycling stability above 97 % for 30 cycles was observed. Also, the long-term stability of CLM electrode was studied by X-ray photoelectron spectroscopy (XPS) and the results showed that the CLM electrode was not prone to surface oxidation after 30 cycles. This study can guide future development of high-performance 2D material composite electrodes for enhancing capacitive deionization efficiency.