Increase In Specific Capacitance Research Articles

Enhancing the quantum yield and electrochemical properties of carbon quantum dots via optimized hydrothermal treatment using cellulose nanocrystals as precursors

Carbon quantum dots (CQDs) are receiving increasing attention due to their tunable redox activity, abundant surface functional groups, and excellent aqueous dispersion. However, their low quantum yield remains a significant impediment to their synthesis and practical application. In the present work, cellulose nanocrystals (CNCs) were utilized as precursors for the optimized hydrothermal synthesis of CQDs. Subsequently, the synthesized CQDs were electrodeposited onto a carbon-coated surface. The influence of hydrothermal temperature and time on the quantum yield and electrochemical properties of CQDs was systematically explored. The successful synthesis of CQDs displayed an average particle size of 5 nm, approximately. The quantum yield was enhanced from 14.35 % to 23.7 % as the hydrothermal temperature increased from 180 °C to 230 °C. Additionally, the electrochemical properties of the composite films were investigated. Electrochemical assessments demonstrated an increase in specific capacitance from 60.4 mF·cm−2 to 65.2 mF·cm−2 with an elevation in temperature from 180 °C to 210 °C. Remarkably, the CQDs displayed higher e CQDs, showcasing their substantial potential for supercapacitor applications.

Probing structural and electrochemical properties of a 2D CoMoO4@hBN nanocomposite as pseudocapacitive electrode for high-performance supercapacitors

The effectiveness of energy storage is largely determined by the electrode material's performance in critical areas. Enhancements in ion transport, cyclic stability, rate capability, and specific capacitance directly boost the supercapacitors' overall performance and broaden their application potential. This study aims to enhance these properties by incorporating hexagonal boron nitride (hBN) into cobalt molybdate (CoMoO4) material in a 1:1 stoichiometric ratio. The CoMoO₄@hBN nanocomposite was synthesized using a hydrothermal method followed by ball milling. The X-ray diffraction (XRD) analysis confirmed the formation of a single-phase CoMoO4@hBN composite, with a significant increase in crystallite size from 18.21 nm in pure CoMoO₄ to 25.6 nm, along with a slight shift in diffraction peaks, indicating enhanced crystallinity and structural defects due to the substitution of oxygen with boron atoms. Raman spectroscopy revealed that the composite retains the characteristic peaks of both CoMoO₄ and hBN, with stable sharp peaks at 936 cm−1 (Mo=O bond) and 1367 cm−1 (E2g peak of hBN) even after 20 depth measurements, confirming successful conjugation and consistent vibrational properties. The X-ray photoelectron spectroscopy (XPS) showed a slight shift in Co 2p and Mo 3d binding energies to higher values, suggesting improved electronic interactions between CoMoO4 and hBN, which could enhance the composite's conductivity. The electrochemical analysis demonstrated that incorporating h-BN significantly boosts the electrode's performance compared to pristine CoMoO4, with about 37 % increase in specific capacitance at 1 A g−1, reduced charge transfer resistance (0.11 Ω), and superior cyclic stability with 96 % capacitance retention after 5000 cycles. These findings indicate that hBN enhances both the electrical conductivity and structural integrity of CoMoO4, positioning the CoMoO4@hBN composite as a promising material for high-performance supercapacitors.

Chitosan/Nitrogen-doped graphene nanocomposite for supercapacitor application

Abstract In this study, we explore the chitosan/nitrogen-doped graphene oxide (CS-NGO) nanocomposite using the hydrothermal method and incorporate it onto carbon paper by a deep coating technique for supercapacitor applications. The incorporation of CS-NGO, a non-toxic and environmentally friendly material, significantly enhances the electrochemical performance. The electrochemical properties are explored by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and impedance spectrum (EIS). The analyses reveal a specific capacitance increase from 2.84 μF cm−2 to 3.96 μF cm−2, a reduction in charge transfer resistance (Rct) from 24.75 Ω to 16.74 Ω, a decrease in Rs resistance from 4.9 Ω to 0 Ω, and a reduction of equivalent series resistance (ESR) from 12.87 Ω to 6.41 Ω. In addition, the results demonstrate remarkable enhancements in energy density and power density and an excellent cyclic stability of 100% over up to 1000 CV cycles of the CS-NGO electrode. These improvements are due to the potential of CS-NGO nanocomposite in developing high-performance, sustainable supercapacitors with the growing demand for green and safe energy storage solutions. This sign of success in this research is due to the new nanocomposite.

Photothermally enhanced ion-transport in solid-state, non-Faradic energy storage devices for sub-freezing operability

The universal direct dependence of ionic mobility on temperature severely restricts the low-temperature operation of energy storage devices. We overcome this limitation by synergizing photothermal conversion with electrochemical energy storage, using non-graphitizable nanocarbon florets (NCF) as multi-functional electrodes. NCF-based supercapacitors leverage the photothermal energy, directing it to the High Internal Phase Emulsion polymer (poly-HIPE) infused ionic conductor [BMIm]-[TFSI], resulting in 15% increase in specific capacitance (Csp) at 30 °C and a 45% at −30 °C. This is the first solid-state energy storage device usable at sub-freezing conditions (< − 4 °C) without compromising its performance. Importantly, the device exhibits identical characteristics at 10 °C (with sunlight) and 30 °C (in the dark), thereby offsetting a temperature difference of 20 °C. Experimental evidences points to the reduction in electrolyte resistance by 86% and 34% in relaxation time constant as the origin of such improved functioning. Furthermore, the advantage of processability is translated to configurational form-factor to efficiently heat the ionic conductor and thereby realise a 15% increase in Csp.

Coal-based Si self-doped disordered porous carbon for supercapacitor electrodes

In preparing activated carbon for coal-based supercapacitors, silicon in coal usually requires removal with hydrofluoric acid, which is neither economical nor environmentally friendly. However, silicon can be used as the anode in lithium batteries due to its high theoretical capacity. So silicon was retained to study its effect on supercapacitors. By retaining silicon without hydrofluoric acid treatment and activating at lower temperature, the prepared Si-doped activated carbon achieved a high specific capacitance of 318.3F/g at 0.5 A/g in the three-electrode test system. Omitting hydrofluoric acid treatment increased the specific capacitance by 49 %. Experimental results show that this 4.92 % silicon doping, mainly CSiO3, is the main reason for the enhancement. Density functional theory (DFT) simulations confirmed that CSiO3 improves double-layer capacitance by localizing surface charge and enhancing electrolyte ion adsorption, while also boosting quantum capacitance. High activation temperatures increase coal-activator reactions but also decrease disorder of the carbon, reducing specific capacitance. Temperature experiments show that the specific capacitance increases and then decreases in the range of 600 ∼ 950 °C, and reaches a peak at 650 °C. This study presents a simple, effective method to enhance supercapacitor performance with silicon-carbon precursors and provides detailed explanation on the capacitance enhancement mechanism for the first time.

Enhancing electrochemical performance of graphene oxide/polyaniline composite through plasma-assisted chemical cross-linking and surface modification

The composite of graphene oxide (GO) and polyaniline (PANI) is a promising electrode material for supercapacitors. A high loading of PANI can provide large specific capacitance, but it is a pervasive challenge to reconcile long-term cycling stability and high-rate discharge. Herein, we focus on a GO/PANI composite with low PANI content (∼25 wt%), developing a stable network of GO with an even distribution of PANI. Moreover, significantly enhanced electrochemical performance is achieved by utilizing plasma technology. The specific capacitance increases by 99 % to 433 F g−1 at 1.5 A g−1 after Argon (Ar) plasma treatment. Even at 15 A g−1, a capacitance retention rate of 91 % is obtained. After 15,000 cycles, the capacitance retention rate is 93 %, surpassing most previously reported GO/PANI composite electrodes. The further assembled all-solid-state supercapacitors can deliver a high energy density of 13.6 Wh kg−1 and exceptional cycling stability. According to results of characterization, it is demonstrated that Ar plasma imparts GO/PANI better surface morphology and achieves etching, reduction of GO, and cross-linking of GO and PANI, thereby activating the electrochemical activities of GO and PANI while ensuring stability. In this regard, the synergistic effects of cross-linking, reduction, and etching, and the mechanism are theoretically illustrated by dynamic differential equations. This work presents plasma processing unique charm for designing graphene-based materials via a customized strategy, exploiting an effectual approach to drive the applications of graphene-based materials in energy storage.

Unraveling the energy storage mechanism in graphene-based nonaqueous electrochemical capacitors by gap-enhanced Raman spectroscopy

Graphene has been extensively utilized as an electrode material for nonaqueous electrochemical capacitors. However, a comprehensive understanding of the charging mechanism and ion arrangement at the graphene/electrolyte interface remain elusive. Herein, a gap-enhanced Raman spectroscopic strategy is designed to characterize the dynamic interfacial process of graphene with an adjustable number of layers, which is based on synergistic enhancement of localized surface plasmons from shell-isolated nanoparticles and a metal substrate. By employing such a strategy combined with complementary characterization techniques, we study the potential-dependent configuration of adsorbed ions and capacitance curves for graphene based on the number of layers. As the number of layers increases, the properties of graphene transform from a metalloid nature to graphite-like behavior. The charging mechanism shifts from co-ion desorption in single-layer graphene to ion exchange domination in few-layer graphene. The increase in area specific capacitance from 64 to 145 µF cm–2 is attributed to the influence on ion packing, thereby impacting the electrochemical performance. Furthermore, the potential-dependent coordination structure of lithium bis(fluorosulfonyl) imide in tetraglyme ([Li(G4)][FSI]) at graphene/electrolyte interface is revealed. This work adds to the understanding of graphene interfaces with distinct properties, offering insights for optimization of electrochemical capacitors.

NiAl LDH nanosheets based on Ag nanoparticles-decoration and alkali etching strategies for high performance supercapacitors

Layered double hydroxides (LDHs) represent a category of two-dimensional layered intercalation materials, showing significant potential as electrode materials for the production of high-energy-density supercapacitors due to their tunable composition, ease of synthetic modification, and low cost. Here, we constructed alkali-etched NiAl LDH-OH nanosheets/Ag nanoparticles (NPs) composite material (Ag@NiAl LDH-OH) for high-performance supercapacitors through a simple solvent-thermal reaction. The alkali treatment is employed to selectively etch some Al3+ ions, generating cation vacancies as active sites for energy storage. Additionally, under the simultaneous influence of strong alkalis and vacancies, the interlayer spacing of LDHs expands, aiding in the promotion of interlayer ion mobility. Meanwhile, the decoration of silver nanoparticles ensures excellent electron conductivity in the NiAl-LDH-OH nanosheets, thereby facilitating improved utilization of the active substance and achieving outstanding rate performance. The Ag@NiAl LDH-OH electrode, when prepared, demonstrates a significant increase in specific capacitance, reaching 1790 F g−1 at a current density of 1 A g−1. This represents approximately 7 times the specific capacitance of the pristine NiAl LDH electrode, with a capacity retention of 79 % even under a high current density of 20 A g−1. Moreover, the assembled asymmetric supercapacitor (ASC) attains a maximum energy density of 138.25 Wh kg−1 at a power density of 700 W kg−1, maintaining 81 % of its initial specific capacitance after 20000 cycles. This research introduces novel pathways for advancing high-energy-density SCs.

Electrical Interface Parameters of PEDOT:PSS: Effect of Electrodeposition Charge Evaluated Under Body Conditions for Neural Electrode Applications

This study explores the influence of the deposition charge of poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) on its electrical interface parameters. For this purpose, PEDOT:PSS was fabricated by electrodeposition on commercial platinum electrodes with the time limited by different charges (1, 3, 6, 9 mC). Further, the electrodes were characterized regarding their electrical interface such as interfacial impedance, potential window, double-layer capacitance, charge storage capacity, and current injection limit under simulated body conditions. The work showed whether and to what extent the change of deposition charge affected the electrical interface parameters of PEDOT:PSS-based platinum electrodes. The electrodes polymerized with 9 mC exhibited a significant increase in specific capacitance, indicating enhanced charge storage capacity. Additionally, this sample demonstrated lower resistance in phosphate-buffered saline, suggesting improved conductivity.

Enhanced brackish water desalination in capacitive deionization with composite Zn-BTC MOF-incorporated electrodes

In this study, composite electrodes with metal–organic framework (MOF) for brackish water desalination via capacitive deionization (CDI) were developed. The electrodes contained activated carbon (AC), polyvinylidene fluoride (PVDF), and zinc-benzene tricarboxylic acid (Zn-BTC) MOF in varying proportions, improving their electrochemical performance. Among them, the E4 electrode with 6% Zn-BTC MOF exhibited the best performance in terms of CV and EIS analyses, with a specific capacity of 88 F g−1 and low ion charge transfer resistance of 4.9 Ω. The E4 electrode showed a 46.7% increase in specific capacitance compared to the E1 electrode, which did not include the MOF. Physicochemical analyses, including XRD, FTIR, FESEM, BET, EDS, elemental mapping, and contact angle measurements, verified the superior properties of the E4 electrode compared to E1, showcasing successful MOF synthesis, desirable pore size, elemental and particle-size distribution of materials, and the superior hydrophilicity enhancement. By evaluating salt removal capacity (SRC) in various setups using an initially 100.0 mg L−1 NaCl feed solution, the asymmetric arrangement of E1 and E4 electrodes outperformed symmetric arrangements, achieving a 21.1% increase in SRC to 6.3 mg g−1. This study demonstrates the potential of MOF-incorporated electrodes for efficient CDI desalination processes.

Structural and Electrochemical Evolution of Water Hyacinth-Derived Activated Carbon with Gamma Pretreatment for Supercapacitor Applications.

This study introduces a gamma pretreatment of water hyacinth powder for activated carbon (AC) production with improved electrochemical properties for supercapacitor applications. The structural and morphological changes of post-irradiation were meticulously analyzed using scanning electron microscopy (SEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). The pretreatment significantly modifies the pore structure and reduces the particle size of the resulting activated carbon (WHAC). Nitrogen adsorption-desorption isotherms indicated a substantial increase in micropore volume with escalating doses of gamma irradiation. Electrochemically, the activated carbon produced from pretreated WH at 100 kGy exhibited a marked increase in specific capacitance, reaching 257.82 F g-1, a notable improvement over the 95.35 F g-1 of its untreated counterpart, while maintaining 99.40% capacitance after 7000 cycles. These findings suggest that gamma-pretreated biomasses are promising precursors for fabricating high-performance supercapacitor electrodes, offering a viable and environmentally friendly alternative for energy storage technology development.

Batch-to-Batch Variation in Laser-Inscribed Graphene (LIG) Electrodes for Electrochemical Sensing.

Laser-inscribed graphene (LIG) is an emerging material for micro-electronic applications and is being used to develop supercapacitors, soft actuators, triboelectric generators, and sensors. The fabrication technique is simple, yet the batch-to-batch variation of LIG quality is not well documented in the literature. In this study, we conduct experiments to characterize batch-to-batch variation in the manufacturing of LIG electrodes for applications in electrochemical sensing. Numerous batches of 36 LIG electrodes were synthesized using a CO2 laser system on polyimide film. The LIG material was characterized using goniometry, stereomicroscopy, open circuit potentiometry, and cyclic voltammetry. Hydrophobicity and electrochemical screening (cyclic voltammetry) indicate that LIG electrode batch-to-batch variation is less than 5% when using a commercial reference and counter electrode. Metallization of LIG led to a significant increase in peak current and specific capacitance (area between anodic/cathodic curve). However, batch-to-batch variation increased to approximately 30%. Two different platinum electrodeposition techniques were studied, including galvanostatic and frequency-modulated electrodeposition. The study shows that formation of metallized LIG electrodes with high specific capacitance and peak current may come at the expense of high batch variability. This design tradeoff has not been discussed in the literature and is an important consideration if scaling sensor designs for mass use is desired. This study provides important insight into the variation of LIG material properties for scalable development of LIG sensors. Additional studies are needed to understand the underlying mechanism(s) of this variability so that strategies to improve the repeatability may be developed for improving quality control. The dataset from this study is available via an open access repository.

Enhancement of energy density for iron MOF-derived composite for aqueous supercapacitor by K3[Fe(CN)6] redox additive electrolyte

Redox additive added aqueous electrolyte attract extensive interest in supercapacitor application. Herein, the electrochemical of the synthesized Fe3O4/Si/GNP composite cathode electrode material was conducted in a two-electrode system via Swagelok cell assembly in the presence of with and without redox additive (0.2 M K3Fe(CN)6 in 1 M Li2SO4). The Fe3O4/Si/GNP composite was successfully synthesized by facile solvothermal method followed by calcination. The structural and morphology investigations of the Fe3O4/Si/GNP composite are conducted via XRD, FESEM, and BET analyses. The synergic effects between the composite material and redox-active ion (Fe2+/Fe3+) in the redox additive electrolyte enhance faradaic reactions, which are utilized to design a high-energy density supercapacitor. The Fe3O4/Si/GNP composite in redox additive electrolyte exhibits a 64.38 % increase in specific capacitance (319.45 F g−1 at 1 A g−1) and a 70.95 % increase in terms of energy density (35.56 Wh kg−1). Redox additive ions in the electrolyte enhance ionic conductivity and facilitate electron transfer across the porous structure of the Fe3O4/Si/GNP composite. The fast reversible kinetics of iron ions enable it to sustain decent cycle stability with a capacitance retention of 73.7 % after 1200 cycles.

Using anodic oxidation for boosting supercapacitive performance of thermally-oxidized cobalt coatings with various morphologies

Metal oxide electrodes for supercapacitors are commonly synthesized through the hydrothermal method. Despite the simplicity and cost-effectiveness of electrodeposition for producing electrode materials, there is a scarcity of literature on electrodeposited electrodes. Previous studies have utilized nitrate-based solutions and subsequent heat-treatment to fabricate these materials without additional treatments to enhance their performance. This research explores the creation of cobalt coatings with varying morphologies (pyramidal, ridge-shaped, powdery, and rough nodular) using electrodeposition from sulfate-based solutions by adjusting deposition parameters. The cobalt coatings were then heat-treated at 550˚C for 3 h to convert them to cobalt oxide, a promising material for supercapacitor electrodes. The study investigates the impact of initial morphology on the structure, phases formed, and supercapacitive properties of the heat-treated coatings. Analysis of XRD and FTIR data indicated that the primary phase post-heat treatment was Co3O4, alongside some CoO. Cyclic voltammetry (CV) measurements in 1 M KOH solution revealed that the powdery coating exhibited the highest specific capacitance of 796±21 mF cm−2 (∼110 F g−1) at a scanning rate of 2 mV s−1, surpassing the heat-treated pyramidal coating by approximately tenfold. These CV findings were corroborated by galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) analyses. Furthermore, the heat-treated coatings underwent anodic oxidation in a 3 M KCl solution for 5 minutes to assess the impact of this lesser-known process on their capacitive behavior. Following anodic oxidation, the ridge-shaped and pyramidal coatings displayed significantly enhanced specific capacitance due to the formation of fine pores and surface modifications. Specifically, the specific capacitance of the ridge-shaped coating surged from 103±4 mF cm−2 (∼11 F g−1) to 1832±64 mF cm−2 (∼201 F g−1) at a scanning rate of 2 mV s−1 after anodic oxidation. Although the rough nodular coating also experienced an increase in specific capacitance, the morphology and electrochemical characteristics of the powdery coating remained relatively stable throughout the study.

Construction of Monolayer Ti3C2Tx MXene on Nickel Foam under High Electrostatic Fields for High-Performance Supercapacitors

Ti3C2Tx MXene, as a common two-dimensional material, has a wide range of applications in electrochemical energy storage. However, the surface forces of few-layer or monolayer Ti3C2Tx MXene lead to easy agglomeration, which hinders the demonstration of its performance due to the characteristics of layered materials. Herein, we report a facile method for preparing monolayer Ti3C2Tx MXene on nickel foam to achieve a self-supporting structure for supercapacitor electrodes under high electrostatic fields. Moreover, the specific capacitance varies with the deposition of different-concentration monolayer Ti3C2Tx MXene on nickel foam. As a result, Ti3C2Tx/NF has a high specific capacitance of 319 mF cm−2 at 2 mA cm−2 and an excellent long-term cycling stability of 94.4% after 7000 cycles. It was observed that the areal specific capacitance increases, whereas the mass specific capacitance decreases with the increasing loading mass. Attributable to the effect of the high electrostatic field, the self-supporting structure of the Ti3C2Tx/NF becomes denser as the concentration of the monolayer Ti3C2Tx MXene ink increases, ultimately affecting its electrochemical performance. This work provides a simple way to overcome the agglomeration problem of few-layer or monolayer MXene, then form a self-supporting electrode exhibiting excellent electrochemical performance.

Preparation of composite based on MXene-Ti3C2 and coconutshell-derived activated carbon for desalination of brackish water

Abstract MXenes is a new two-dimensional material which is gaining more attention in recent years for applications in catalysis, energy storage, and environmental remediation. In this study, MXene-Ti3C2 is synthesized from precursor MAX-Ti3AlC2 via etching method and then combined with coconutshell-derived activated carbon to provide a highly conductive and porous composite. The composite will be later employed as electrode materials in capacitive deionization for water desalination. The results have shown an increase in specific capacitance by 3.7 times in the composite (0.5 wt% MXene-Ti3C2) when compared with pure activated carbon. These promising results have proved the possibility to use MXenes-based composites for desalination and other treatment techniques for salted water.

Enhanced Supercapacitive Performance in Catalyst‐Free Binary Composite SnO2–RuO2 Nanostructured Thin Films for Symmetric Supercapacitor Device

In the present work, thin film electrodes of ruthenium oxide (RuO2), tin oxide (SnO2), and their composite SnO2–RuO2 are deposited on 304 stainless steel substrates using pulsed laser deposition (PLD). These nanostructured electrodes are then evaluated for their suitability in electrochemical energy storage applications. A symmetric supercapacitor device (SSD) is constructed using the SnO2–RuO2 composite electrodes. Compared to individual SnO2 and RuO2 electrodes, the composite electrodes exhibit enhanced specific capacitance and cycle life. This improvement is attributed to modifications in surface morphology and electronic properties. This modified surface morphology of the composite electrode, creates favourable conditions for electrolyte interaction and ion transport, ultimately contributing to the observed increase in specific capacitance. Specifically, the composite electrode demonstrates a specific capacitance of 170.2 Fg−1 at a current density of 0.1 mA cm−2, outperforming SnO2 (37.4 Fg−1). The SnO2–RuO2//SnO2–RuO2 SSD exhibites a specific capacitance of 70.0 Fg−1 at a current density of 0.1 mA cm−2, coupled with energy density and power density values of 19.05 Wh kg−1 and 645 W kg−1, respectively, within a voltage window of 1.4 V. The SSD displays an impressive capacitive retention of 81.27% over 10 000 cycles, indicating its potential for practical energy storage applications.

Green Plasma Enhanced Synthesis of Multi-Phase NiMnO3 Cathode for Aqueous Zn-Ion Batteries

Rechargeable Zn-ion batteries have the potential to address the need for cheap and widely accessible energy storage. Metal-doped manganese oxide cathodes are a common and effective choice for Zn-ion batteries. Zn-ion battery development can be advanced by overcoming the poor cycle life that many metal-doped Mn-oxide cathodes suffer from. Plasma-treated water (PAW) is created using low input power of 0.145 kWh per liter of PAW and is used to accelerate the reduction and precipitation of MnO4 − and nickel acetate (Ni(Ac)) to form a multiphase NiMnO3 electrode with Ni2+ and Ni3+ doped into the MnO6 octahedra, which exhibits capacitance dominated charge storage mechanisms. The electrode shows initial specific capacitance of 60.1 F g−1 and a capacitance retention of 100.8% after 10,000 cycles and 92.2% after 12,000 cycles. The beneficial layer of nanoflake morphology is formed during cycling, which causes a rapid increase in specific capacitance due to the larger electrochemically active surface area and the associated surface adsorption-based (pseudo-capacitive) type charge storage. We also demonstrate the capability of our multiphase NiMnO3 electrode to be coupled with a Zn metal anode in a battery cell which exhibits 330 mAh g−1 peak specific capacity and capacity retention of 63.8% after 380 cycles.

Enhancing the specific capacitance of α-MnO2 through quenching-induced changes in the crystal phase structure

The development of materials with high electrochemical performance as response to the energy demand leads to the development of methods for enhancing the specific capacity of energy storage devices, such as heat treatment, which is used to modify the structure and electrochemical performance of materials. This paper reports the enhancement of specific capacitance of α-MnO2 through the high-volume cell (HVC) induced by the quenching technique. Analysis of the transformation and structure of HVC was carried out by a combination of thermal gravimetric analysis and differential scanning calorimetry (TGA–DSC) in addition to X-ray diffraction (XRD), while the characterization of morphology, crystal structure, and capacitance were performed through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and cyclic voltammetry (CV). The α-MnO2 quenched at 437 °C promotes a structural modification that enables an increase in cell volume of 10.6% and an increase in specific capacitance of 20%. The quenching technique would be an attractive methodology to improve the electrochemical performance of materials for energy storage.

Scalable electrochemical grafting of anthraquinone for fabrication of multifunctional carbon fibers

Carbon fiber electrodes were prepared by grafting anthraquinone molecules via a scalable electrochemical approach which simultaneously increased interfacial and electrochemical capacitance properties. In this work, anthraquinone diazonium salts were synthesized and grafted onto carbon fiber tows at various concentrations. These modified fibers were subsequently evaluated mechanically and electrochemically to analyze their suitability in structural supercapacitors. Compared to control fibers, the grafted anthraquinone groups resulted in a 30% increase in interfacial shear strength (IFSS) and 6.6× increase in specific capacitance. Industry application was also a focus thus carbon fibers were also modified with in-situ generated diazonium salts to determine the applicability to an in-line industrial process. Specifically, potentiostatic functionalization of fibers with in-situ generated diazonium salts AQ-1 and AQ-2, showed 3× and 4.3× increase in specific capacitance, respectively, relative to unmodified carbon fiber (CF). We expect that implementing a scalable method to introduce a conductive and electrochemically active covalently bound surface chemistry layer onto carbon fiber exhibits a higher specific capacitance than carbon fiber grafted with most other small molecules reported in literature. This will open new avenues for manufacturing multifunctional and high-performance fibers with tailored properties for specific/targeted applications.