Symmetric Supercapacitor Device Research Articles

Effect of Substrate Temperature on the Electrochemical and Supercapacitance Properties of Pulsed Laser-Deposited Titanium Oxynitride Thin Films

Abstract Electrocatalytically active titanium oxynitride (TiNO) thin films were fabricated on commercially available titanium metal plates using a pulsed laser deposition (PLD) method for energy storage applications. The elemental composition and nature of bonding were analyzed using x-ray photoelectron spectroscopy (XPS) to reveal the reacting species and active sites responsible for the enhanced electrochemical performance of the TiNO electrodes. Symmetric supercapacitor devices were fabricated using two TiNO working electrodes separated by an ion-transporting layer to analyze their real-time performance. The galvanostatic charge-discharge studies on the symmetric cell have indicated that TiNO films deposited on the polycrystalline titanium plates at lower temperatures are superior to TiNO films deposited at higher temperatures in terms of storage characteristics. For example, TiNO films deposited at 300°C exhibited the highest specific capacity of 69 mF/cm2 at 0.125 mA/cm2 with an energy density of 7.5 Wh/cm2. The performance of this supercapacitor (300°C TiNO) device is also found to be ∼ 22 % better compared to that of a 500°C TiNO supercapacitor with a capacitance retention ability of 90% after 1000 cycles. The difference in the electrochemical storage and capacitance properties is attributed to the reduced leaching away of oxygen from the TiNO films by the Ti plate at lower deposition temperatures, leading to higher oxygen content in the TiNO films and, consequently, a high redox activity at the electrode/electrolyte interface.

High‐Performance NiCo2O4/Graphene Quantum Dots for Asymmetric and Symmetric Supercapacitors with Enhanced Energy Efficiency

AbstractFor the sustainable growth of future generations, energy storage technologies like supercapacitors and batteries are becoming more and more common. However, reliable and high‐performance materials’ design and development is the key for the widespread adoption of batteries and supercapacitors. Quantum dots with fascinating and unusual properties are expected to revolutionize future technologies. However, while the recent discovery of quantum dots honored with a Nobel prize in Chemistry, their benefits for the tenacious problem of energy are not realized yet. In this context, herein, chemical‐composition tuning enabled exceptional performance of NiCo2O4(NCO)/graphene quantum dots (GQDs) is reported, which outperform the existing similar materials, in supercapacitors. A comprehensive study is performed on the synthesis, characterization, and electrochemical performance evaluation of highly functional NCO/GQDs in supercapacitors delivering enhanced energy efficiency. The high‐performance, functional NCO/GQDs electrode materials are synthesized by the incorporation of GQDs into NCO. The effect of variable amount of GQDs on the energy performance characteristics of NCO/GQDs in supercapacitors is studied systematically. In‐depth structural and chemical bonding analyses using X‐ray diffraction (XRD) and Raman spectroscopic studies indicate that all the NCO/GQDs composites crystallize in the spinel cubic phase of NiCo2O4 while graphene integration evident in all the NCO/GQDs. The scanning electron microscopy imaging analysis reveals homogeneously distributed spherical particles with a size distribution of 5–9 nm validating the formation of QDs. The high‐resolution transmission electron microscopy analyses reveal that the NCOQDs are anchored on graphene sheets, which provide a high surface area of 42.27 m2g−1 and high mesoporosity for the composition of NCO/GQDs‐10%. In addition to establishing reliable electrical connection to graphene sheets, the NCOQDs provide reliable 3D‐conductive channels for rapid transport throughout the electrode as well as synergistic effects. Chemical‐composition tuning, and optimization yields NCO/GQDs‐10% to deliver the best specific capacitance of 3940 Fg−1 at 0.5 Ag−1, where the electrodes retain ≈98% capacitance after 5000 cycles. The NCO/GQD‐10%//AC asymmetric supercapacitor device demonstrates outstanding energy density and power density values of 118.04 Wh kg−1 and 798.76 W kg−1, respectively. The NCO/GQDs‐10%//NCO/GQDs‐10% symmetric supercapacitor device delivers excellent energy and power density of 24.30 Wh kg−1 and 500 W kg−1, respectively. These results demonstrate and conclude that NCO/GQDs are exceptional and prospective candidates for developing next‐generation high‐performance and sustainable energy storage devices.

Synthesis and Investigation of Electrochemical Studies on Thulium Tellurite (TmTeO3) for Supercapacitor Electrode Application

Thulium tellurite (TmTeO[Formula: see text] is synthesized by hydrothermal method. It exhibits nearly cuboid-shaped particles along with triangular particles. TmTeO3 is found to be monoclinic. The energy gap is 5.87 eV, the Urbach energy value is 0.287 eV and the refractive index is 1.881. The size of the particle is determined as 107 nm. Optical transitions between energy levels assign absorption and emission peaks. Tm, was found in the oxide matrix as Tellurite. Magnetic susceptibility between 20 K and 300 K decreases with temperature, reaches saturation and aligns all Thulium spins. M–H curve confirms paramagnetic nature at 300 K and feeble ferromagnetic nature at 77 K. Cyclic voltammogram and chronopotentiometry analysis exhibit pseudo-capacitive behavior. The potential window is 0.82. Specific capacitance is found to be 87 F/g. Chronopotentiometry analysis shows 55 F/g specific capacitance. Impedance analysis shows a pseudo-capacitive nature. TmTeO3 symmetrical supercapacitor device is fabricated with potential window of 1.52 V. A specific capacitance of 37.75F/g at 1 A/g, energy density 6.055Wh kg[Formula: see text] and power density 760.99W kg[Formula: see text] was achieved. Impedance analysis shows low series resistance of 2.567[Formula: see text] and charge transfer resistance of 0.473[Formula: see text]. Cyclic performance with 80% specific capacitance retention is observed after 5000 cycles. The TmTeO3 symmetric supercapacitor electrodes possess good electrochemical properties due to wider potential window, long cycle stability and notable energy density.

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.

Effect of air-annealing on the structure, surface morphology, and supercapacitive properties of the 2D-BiOCl nanosheets

Upright-standing nanosheets of bismuth oxychloride (BiOCl), synthesized via a facile chemical synthesis method and air-annealed from 50 to 600 ℃ temperatures (named BOC-50-600), are envisaged as electrochemical supercapacitor electrodes. These electrodes are initially screened for their surface morphology, elemental configuration, phase purity, and binding energy by various means. Due to changes in the surface morphology, phase, charge transfer resistance, and binding energy, the one annealed at 150 ℃ i.e., BOC-150 has offered targeted supercapacitive performance due to quasi-faradaic redox reactions in 6M KOH electrolyte solution. The specific capacitance of the BOC-150 electrode, measured at 1.40–5.0A/g current densities, varies from 264.6 to 95F/g. The as-assembled BOC-150//BOC-150 symmetric supercapacitor device (SSD) demonstrates an efficient supercapacitive performance with a maximum 86.87Wh/kg energy density and 3735W/kg power density. Additionally, the as-designed SSD endows an admirable capacity retention of 81.6% for 5000 charge-discharge cycles, approving moderate chemical stability and considerable mechanical robustness for use in commercial electronic items.

Fabrication of highly flexible, wearable, free-standing symmetric supercapacitors with high voltage operation enabled by hierarchical graphene/cerium oxide/polypyrrole hybrid films

Flexible, free-standing supercapacitors play a significant role in the development of future wearable energy storage devices. Herein, we successfully fabricated the highly flexible and free-standing graphene/cerium oxide/polypyrrole hybrid films by thermal reduction of graphene oxide (GO) followed by the sol–gel synthesis of CeO2 and then the addition of PPy. By regulating oxygen functional groups in GO, the electronic conductivity and electroactive sites of the hybrid films are significantly controlled, leading to enhanced energy storage capability. Finally, a symmetric flexible supercapacitor (FSC) device was developed using the prepared films as electrodes. Resulting, the integrated symmetric GO-400/CeO2/PPy FSC manifests excellent areal capacitance of 49.0 mF cm−2 at 1 mA cm−2, with a durability of 83.1 % over 10,000 cycles. Specifically, the FSC exhibited capacitance retention of 77.2 % after 10,000 cycles under bending state with exceptional rate ability. Meanwhile, an impressive energy density of 19.69 µW h cm−2 was attained at a power density of 0.85 mW cm−2. Evidently, the synergistic interactions between GO and PPy nanosheets, along with CeO2 favour the rapid electron movement of electrode material for next-generation wearable, portable electronics.

Manipulating the overall capacitance of hierarchical porous carbons via structure- and pore-tailoring approach

Herein, we present pore architecture-tailorable porous carbons through a time-adjustable hydrothermal reaction and subsequent KOH chemical activation method. Accordingly, platanus spiky (Ps) fruits, taro (T) roots, and green bell peppers (Pp) biowaste substrates were utilized as sustainable precursors to construct novel hierarchical porous carbons (HPCs) with highly interconnected porous frameworks and smart micro/meso/macroporous architecture for supercapacitors. The heterogeneous feedstocks were pre-carbonized under hydrothermal conditions for different hold durations (12 h, 24 h, 36 h) at 200 °C. The optimized Ps-24h material exhibits a high capacitance of 371.6 F g−1 at 1 A g−1 in an aqueous Na2SO4 electrolyte and an outstanding rate performance (94% capacitance retention after 10,000 charge-discharge cycles). Surprisingly, the specific gravimetric capacitance of HPCs can be significantly manipulated by establishing a high-performance redox electrolytic system. In particular, the tailored Ps-24h-based electrode delivers a superior capacitance of 843 F g−1 at 1 A g−1 with an exceptional rate capability (64.7% capacitance retention from 1 to 20 A g−1 in K3[Fe(CN)6]/Na2SO4 electrolyte). Consequently, the as-integrated Ps-24h//Ps-24h symmetric supercapacitor device with a working voltage of 1.8 V presents enhanced energy/power outcomes (63.8 Wh kg‒1/900.2 W kg‒1) with remarkable long-term cyclic durability (90.4% capacitance retention after 15,000 cycles) in a redox electrolytic system.

A novel carbon microtubes derived from the used surgical face mask for the Ni-F/FMs symmetric supercapacitor device

The emergence of COVID-19 had an unprecedented impact on society, leading to the widespread usage and disposal of surgical face masks (FMs). This work contributes to repurposing FMs into carbon materials through simplified solvothermal-assisted pyrolysis processes for supercapacitor applications. XRD and FESEM were employed to investigate the materials' microstructural and micrographic characteristics. The FM 700 has a specific capacitance value of 182.61 Fg−1, more significant than the other produced sample in the 1 M KOH electrolyte. The symmetric solid-state supercapacitor with a maximum capacitance of 92.67 Fg−1 is constructed under perfect circumstances. After 10,000 cycles, FM 700-SSSD maintained 89 % of its value. Turning FMs into carbon materials for energy storage applications is made more accessible by this method and also prevents the environment from pollution.

Anion substitution-induced CuCoSe hollow nanotubes as multifunctional electrode materials for supercapacitors and overall water splitting

Developing highly efficient non-noble-metal electrode materials for energy storage and conversion is crucial for advancing sustainable and renewable energy. In this study, a facile and effective anion substitution-induced approach was designed to synthesize uniform CuCoSe hollow nanotubes. Impressively, the obtained CuCoSe hollow nanotubes reach an exceptional mass-specific capacitance of 2,853.1F·g−1 at 10 A·g−1, with intriguing rate capability and desirable capacitance retention after 5,000 cycles. The assembled CuCoSe//CuCoSe symmetrical supercapacitor device exhibits a high energy density of 218.9 Wh·kg−1 at a power density of 4,000 kW·kg−1. Furthermore, the CuCoSe hollow nanotubes show exceptional performances in both oxygen and hydrogen evolution reactions, necessitating low overpotentials of 94.4 and 33.4 mV at 10 mA·cm−2. When used as a bifunctional electrocatalyst, the assembled CuCoSe||CuCoSe electrolytic cell affords a low cell voltage of 1.40 V to drive 10 mA·cm−2, significantly superior to other commercial electrolyzers and most reported bifunctional electrocatalysts. Experimental and density functional theory calculations suggest that selenides substituted CuCo-layered double hydroxides can greatly enhance the electrochemical performances. This work will be beneficial for the design of the next generation of energy storage and conversion technologies.

Electrodeposited three-dimensional hierarchical architecture of MgO anchored with Ag nanoparticles for high-performance symmetric supercapacitors

A blossom-like, three-dimensional (3D) hierarchical architecture of MgO anchored with silver nanoparticles (Ag NPs) is developed using a simple galvanostatic electrodeposition method. This study shows how electrochemical performance is improved by the incorporation of Ag NPs within a 3D framework. The 3D blossom-like scaffold comprises thin 2D petals, whose porous lace-like patterns provide a large surface area and many channels for the rapid diffusion of electrolyte ions. The anchored Ag NPs increase the electrical conductivity of the MgO structure and enhance redox reactions. An optimum Ag loading of 10 vol% on MgO (MgO@Ag-10) affords a 100-fold enhancement in specific capacitance over that of MgO. This hybrid MgO@Ag-10 electrode on a stainless-steel substrate yields a specific capacitance of 388.6 F.g−1 (134.85 mF.cm−2) at a current density (CD) of 1 mA.cm−2, whereas pure MgO delivers only 3.72 F.g−1 (3.1 mF.cm−2) at the same CD in a three-electrode system. The MgO@Ag-10 electrode also exhibits 88.6 % capacitance retention over 5000 charge–discharge cycles. A symmetric supercapacitor device comprising two MgO@Ag-10 electrodes exhibits a specific capacitance of 42 F.g−1, an energy density of 23.33 Wh.kg−1, and a power density of 8000 W.kg−1 at 4 mA.cm−2 in aqueous KOH.

N, O self-doped porous carbon derived from distiller's grains for high performance supercapacitors

Improving the charge storage capacity of carbon materials derived from biomass waste is an important aspect for their practical applications as supercapacitor electrodes. A reasonable design of heteroatom-doped carbon materials derived from industrial distiller 's grains can significantly enhance the efficacy of the supercapacitor. Therefore, a distiller's grain-derived (DG) N/O self-doped activated carbon (DG-5-X) was developed for use in supercapacitors. The incorporation of heteroatoms into porous carbon materials can facilitate enhanced electrode-to-electrolyte interaction resulting in improved pseudo-capacitance, thereby enhancing the electrochemical performance. A remarkable 345.2 F g−1 specific capacitance was demonstrated in a three-electrode system employing DG-5–6 (with N and O heteroatom contents of 1.62 % and 19.27 %, respectively) as the electrode in a 6 M KOH electrolyte solution (at 1 A g−1). In addition, a symmetric coin-type supercapacitor (SSC) device was developed, which demonstrated excellent cyclic stability and a competitive energy density of 12.2 Wh kg−1 (at a 348.8 W kg−1 power density). SSC retained 95.6 % of the capacitance after 5000 cycles at 5 A g−1. In summary, the distiller’s grains as a raw material show great potential in the development of carbon-based energy storage materials that display outstanding electrochemical performance.

Nitrogen and oxygen self-doped hierarchical porous carbon nanosheets derived from turmeric leaves for high-performance supercapacitor

It is a formidable challenge to develop efficient and low-cost nanostructured carbonaceous materials for electrochemical energy storage application. Herein, a hierarchical porous carbon nanosheet is successfully synthesized in a facile manner from turmeric leaves by a two-step chemical activation strategy using KOH activator. The biomass-derived interconnected two-dimensional (2D) carbon framework prepared at 900 °C presents high self-doped N (11.42 at%) and O contents (7.77 at%) together with specific surface area and pore volume of 541 m2/g and 0.47 cm3 g−1, respectively. Consequently, the resultant electroactive functional material shows a specific capacitance of 389 and 310 F/g at a current density of 1 A/g in acidic and neutral electrolytes, respectively. Additionally, an assembled symmetric supercapacitor device in Na2SO4 electrolyte delivers good capacitance retention of 90 % after 5000 consecutive charge–discharge cycles along with high specific energy (39.44 Wh kg−1at specific power of 0.49 kW kg−1). This work provides a cost-effective, eco-friendly and sustainable outlook to prepare high-valued porous carbons from reliable biomass sources for high-performance supercapacitor application.

Self-healable PVA-Borax-K2SO4 hydrogel electrolyte for flexible symmetric supercapacitors

The self-healing hydrogel materials are formed from the reaction between polyvinyl alcohol (PVA) and sodium tetraborate (Borax). The O-B-C vibration peak from the FT-IR spectrum is used to confirm the formation of the self-healing hydrogel structure. With 0.5 M concentration K2SO4, the resistivity of PVA-Borax-K2SO4 material is evaluated by Bode cure and obtained at 4.13 Ω.cm. With the improvement in hybrid structure, the flexible supercapacitor (FSS) devices were fabricated from two carbon fiber fabrics as symmetric electrodes with a self-healing hydrogel material (PVA-Borax-K2SO4) as electrolyte and separator. The electrochemical performances of flexible symmetric supercapacitor (FSS) devices are measured by cyclic voltammetric, charge/discharge, and impedance tests. The specific capacitance of FSS obtained 1.725 mF/cm2 at 0.05 mA/cm2 discharge current. Moreover, the stability of the FSS device attained confirmation by the comparison of the specific capacitance at 2 and 50 cycles.

Unlocking the potential of magnetic bio-char as a low-cost cathode material for the supercapacitor application

Modification of biochar is an intriguing idea to enhance the electrochemical performance of biochar-based electrode materials for supercapacitors. Herein, magnetic biochar (MBC) was successfully prepared via low-cost pyrolysis techniques. The as-synthesized MBC has a carbon-rich structure and a higher surface area of 14.14 m2 g−1 which makes it suitable for use as an electrode. The as-fabricated optimized composite (MBC) exhibits amazing super capacitive performance in terms of high specific capacitance (1397 F/g), good cycle stability, and magnificent rate capability when first served as electrodes. Moreover, the symmetric supercapacitor device was synthesized by using MBC as a cathode and anode. Because of their porous structure, complementary potential windows (0–1.3 V) of two electrodes, rate capabilities, and high specific capacitance, the device exhibits desirable electrochemical properties. At 900 W/kg of power density, the symmetric supercapacitor has an energy density of 12.2 Wh/kg. Based on these optimistic results, we need to do further research to create high-energy and power-density devices for practical applications.

Smart Energy Storage: W18O49 NW/Ti3C2Tx Composite-Enabled All Solid State Flexible Electrochromic Supercapacitors.

Developing a highly efficient electrochromic energy storage device with sufficient color fluctuation and significant electrochemical performance is highly desirable for practical energy-saving applications. Here, to achieve a highly stable material with a large electrochemical storage capacity, a W18O49 NW/Ti3C2Tx composite has been fabricated and deposited on a pre-assembled Ag and W18O49 NW conductive network by Langmuir-Blodgett technique. The resulting hybrid electrode composed of 15 layers of W18O49 NW/Ti3C2Tx composite exhibits an areal capacitance of 125mFcm-2, with a fast and reversible switching response. An optical modulation of 98.2% can be maintained at a current density of 5mAcm-2. Using this electrode, a bifunctional symmetric electrochromic supercapacitor device having an energy density of 10.26µWhcm-2 and a power density of 0.605mWcm-2 is fabricated, with high capacity retention and full columbic efficiency over 4000 charge-discharge cycles. Meanwhile, the device displays remarkable electrochromic characteristics, including fast switching time (5s for coloring and 7s for bleaching), and a significant coloration efficiency of 116cm2C-1 with good optical modulation stability. In addition, the device exhibits significant mechanical flexibility and fast switching while being stable over 100 bending cycles, which is promising for real-world applications.

Synthesis of 3D rice-like BiOCl battery-type electrode material and evaluation of their electrochemical performance in a symmetrical supercapacitor device configuration

3D porous rice-like BiOCl nanostructure was prepared via solvothermal technique with sodium chlorate as a surfactant which serves as electrode material for the supercapacitor applications. The prepared nanoparticles supported on nickel foam textile exhibit high battery-type charge storage ability in a 3 M KOH aqueous electrolyte solution. The dominance of the battery-type charge storage mechanism of the BiOCl electrode was confirmed through the CV study. Furthermore, the GCD study revealed a good specific capacity of 501 C/g at 0.5 A/g current density and cycle stability of 80% over 2500 cycles. In the presence of a 3 M KOH electrolyte, a symmetric supercapacitor device was constructed with two identical 3D rice-like BiOCl electrodes. This configuration unveiled an impressive energy density of 21.8 Wh/kg at 772.5 W/kg power density. To illustrate its practical viability, two BiOCl/BiOCl symmetric devices were connected in series, successfully powering a red LED for approximately 50 s with high light intensity. This underscores the practical potential of the 3D rice-like BiOCl electrode in energy storage systems. In order to maximize the potential of BiOCl material in the future, the focus could be shifted towards mitigating the challenge of potential drop. This hurdle could be tackled by fabricating nanocomposites of BiOCl incorporated with conductive polymers and graphene oxide, thus elevating its overall performance.

Biopolymer pectin with calcium ion crosslinker as biocompatiable electrolyte for energy storage applications

Biopolymer electrolyte-based electrochemical devices for charge storage, such as supercapacitors and rechargeable batteries, attract wide attention. This study proposes that thin, transparent, and flexible polymer electrolytes can be fabricated using pectin, poly (ethylene glycol) (PEG), and calcium chloride (CaCl2) by solvent casting. CaCl2 plays a vital role as a crosslinker to form the film. The developed pectin/CaCl2 (PeO) and PEG/pectin/CaCl2 (PPe) polymer films are subjected to Fourier transform infrared analysis (FTIR) to confirm polymer matrix formation with the salt ions. The biopolymer membrane's glass transition temperature (Tg) is analyzed using differential scanning calorimetry (DSC). Symmetric supercapacitor devices were fabricated using activated carbon (AC) as electrode material, functionalized carbon fiber as a current collector, and pectin polymer films (PeO and PPe) as a gel electrolyte/separator. The symmetrical device with AC as the electrode and PPe as the electrolyte [AC||PPe||AC] exhibited a specific capacitance of 879 mF cm−2 at 15 mA cm−2, which is considerably higher than the similar device with PeO as electrolyte [AC||PeO||AC]. The cyclic stability of the [AC||PPe||AC] supercapacitor device was 83 % over 5000 cycles. Three supercapacitor devices connected in series is capable to glow 5 light-emitting diodes (LEDs). Good storage and stability indicate that the PPe is suitable as a gel polymer electrolyte material. This polymer electrolyte has excellent prospects in practical applications of all-solid-state, flexible, portable, and biocompatible energy storage devices.

Stoichiometrically Optimized Electrochromic Complex [V2 O2+ξ (OH)3-ξ ] Based Electrode: Prototype Supercapacitor with Multicolor Indicator.

The systematic structure modification of metal oxides is becoming more attractive, and effective strategies for structural tunning are highly desirable for improving their practical color-modulating energy storage performances. Here, the ability of a stoichiometrically tuned oxide-hydroxide complex of porous vanadium oxide, namely [V2 O2+ξ (OH)3-ξ ]ξ = 0:3 for multifunctional electrochromic supercapacitor application is demonstrated. Theoretically, the pre-optimized oxide complex is synthesized using a simple wet chemical etching technique in its optimized stoichiometry [V2 O2+ξ (OH)3-ξ ] with ξ=0, providing more electroactive surface sites. The multifunctional electrode shows a high charge storage property of 610Fg-1 at 1Ag-1 , as well as good electrochromic properties with high color contrast of 70% and 50% at 428 and 640nm wavelengths, faster switching, and high coloration efficiency. When assembled in a solid-state symmetric electrochromic supercapacitor device, it exhibits an ultrahigh power density of 1066mWcm-2 , high energy density of 246mWhcm-2 , and high specific capacitance of 290mFcm-2 at 0.2mAcm-2 . A prepared prototype device displays red when fully charged, green when half charged, and blue when fully discharged. A clear evidence of optimizing the multifunctional performance of electrochromic supercapacitor by stoichiometrical tuning is presented along with demonstrating a device prototype of a 25cm2 large device for real-life applications.

Interfacial regulation of biomass-derived carbon towards high-performance supercapacitor

Interfacial regulation for carbon-based materials plays critical role for supercapacitive performance improvement and the strategies about introducing heteroatomic groups and tuning specific surface area can be proposed to effectively address the low specific capacitance issues. Thus, the approaches about activation treatment with nitric acid (APC-H800) and copper chloride (APC-C800) for biomass-derived carbon materials have been raised and systematically investigated. Consequently, though the above chemical activation treatment, the oxygen and nitrogen functional groups can be introduced for APC-H800. Meanwhile, the specific surface area of APC-C800 has been significantly increased. Significantly, the upper specific capacitance of 384 F g−1 and 423 F g−1 for APC-H800 and APC-C800 electrodes can be achieved at a current density of 1.0 A g−1, what matters more is that two symmetric devices offer superior energy density and desirable cycling stability (no decrease that occurs after 10,000 cycles) are successfully assembled by employing APC-H800 and APC-C800 electrodes, respectively. More significantly, desirable energy density about 11.18 Wh kg−1 and 12.5 Wh kg−1 at 249.98 W kg−1 and 250 W kg−1 have been achieved for the symmetric supercapacitor devices of APC-H800//APC-H800 and APC-C800//APC-C800. These modification strategies shed insight into the sensible design of a further stage of advanced art carbon electrodes for powerful performance supercapacitors.

Exploring optical and electrochemical studies on thulium selenite (TmSeO3)

Abstract Thulium selenite (TmSeO3) has been synthesized by precipitation method. It shows interesting smooth surface with nearly non-symmetric texture similar to water droplets spreading on hydrophobic surface. TmSeO3 is found to be monoclinic structure with lattice parameters a = 5.919±0.01 Å, b = 12.422±0.01 Å, c = 8.717±0.01 Å, α = γ = 90°, β = 106.01° and V = 616.1 Å3. Fourier transform infrared spectroscopy confirms the presence of Tm–Se bonding. X-ray photo emission spectrum confirmed the presence of thulium, selenium and oxygen in the samples in oxide form. Magnetic study between 300 and 20 K, shows decrease of magnetic moment with temperature, then reaches saturation and aligns all thulium spins. This results cooperative interaction of thulium spins. M–H curve at 300 K confirms the paramagnetic nature of sample. Cyclic voltammogram of three electrode system, manifests electric double layer capacitance with a potential window of 0.55 V. Specific capacitance is 102 F/g. Chronopotentiometry analysis shows 75 F/g specific capacitance, 11 Wh kg−1 energy density, and 275 W kg−1 power density. Impedance analysis confirms electric double layer capacitor behavior. Hence, TmSeO3 electrode based symmetric supercapacitor device was successfully fabricated and tested by two electrode configuration in aqueous electrolyte of KOH. A specific capacitance of 64.60 F/g at 1 A/g within a potential window of 1.85 V was achieved. Impedance analysis also confirms electric double layer capacitor nature with low series resistance of 0.2596 Ω and charge transfer resistance of 1.6352 Ω. The improved cycling performance after 4000 cycles is 51.5 % specific capacitance retention. Thus, symmetric supercapacitor electrodes based TmSeO3 materials are expected to have good electrochemical properties and good stability for energy storage and conversion applications. Furthur, optical parameters 5.28 eV energy gap, 0.4924 eV Urbach energy value and 1.959 refractive index are determined.