Galvanostatic Charge Discharge Research Articles

Enhancing Supercapacitor Performance of NiCoMn‐Layered Double Hydroxide with Ag–Citrate/Polyaniline Nanocomposites

Layered double hydroxide (LDH) has a layered structure, which makes it a strong candidate for supercapacitors (SC) due to its high surface area. However, they suffer from low conductivity due to insufficient charge transfer across their layers. This research aims to overcome this obstacle by introducing conductive channels among the layers by the addition of Ag–citrate and polyaniline (PANI). Consequently, five electrodes (S1–5) were made from NiCoMn LDH (referred to as LDH henceforth) and 2:1 Ag–citrate and PANI composite (Ag/PANI) in different ratios and made into electrodes. Electrochemical analysis revealed successful improvement in the performance of LDH as the fraction of Ag/PANI increased until it equaled Ag/PANI where the highest specific capacitance of 617 F g−1 was obtained, which is 12% greater than the value for solely LDH electrode (550 F g−1). A device was fabricated with the best electrode (S3) and activated carbon electrode, which demonstrated energy densities and power densities of 41 WhKg−1 and 412.5 W Kg−1 and 14 WhKg−1and 8250 W Kg−1 at 0.5 and 10 A g−1 current densities, respectively. It also exhibited a capacitive retention of about 75% at 3000 galvanostatic charge–discharge cycles. These results encourage the use in of NiCoMn LDH, in a 1:1 ratio with Ag/PANI in SCs due to its remarkable performance.

Facile synthesis and characterization of zinc molybdate (ZnMoO4) nanosheets for electrochemical supercapacitor application

Abstract This study explores the synthesis and characterization of zinc molybdate (ZnMoO4) nanosheets with emphasis on their potential application for energy storage devices particularly supercapacitors. The synthesis of ZnMoO4 nanosheets was done through co-precipitation followed by examination of their structure, morphology, optical, thermal behaviour and electrochemical performance by various characterization techniques. X-ray diffraction (XRD) analysis confirmed that the formation of monoclinic ZnMoO4 phase with the average crystallite size 17.93 nm. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) revealed that this material had nanosheets-like structure which helps to increase ion transport and surface area; these two factors are essential for enhancing the material’s supercapacitor efficacy. The semiconductor characteristics were determined using UV–Visible diffuse reflectance spectroscopy (UV-DRS) which indicated a band gap energy of 4.2 eV. Fourier transform infrared (FTIR) analysis confirmed that the presence of Zn–O and Mo–O bonds in their crystal lattice. Thermogravimetric analysis (TGA) showed that the ZnMoO4 nanosheets had thermal stability since they experienced only a slight mass loss of 2.57 % up to 800 °C. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests were undertaken to find out the specific capacitance and the value is 618 F g⁻1 at a current density of 1 A g⁻1.

Investigation of Bi2MoO6/MXene nanostructured composites for photodegradation and advanced energy storage applications

This study presents nanostructured composite Bi2MoO6/MXene heterostructure by using hydrothermal method for photodegradation of the congo-red dye and also for energy storage devices. X-ray diffractometer (XRD), High Resolution Transmission Electron Microscopy (HRTEM), Field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) were performed to examine the structural properties along with surface area and porosity of the material. Due to addition of MXene the larger surface area and improved pore size help to quickly break down additional organic pollutants by adsorbing them. The band gap of Bi2MoO6/MXene nanostructured composite reduced to 2.4 eV suggesting transfer of electrons from VB to CB. Bi2MoO6/MXene exhibits a high (92.3%) photocatalytic degradation rate for a duration of 16 min which was verified using UV-visible spectroscopy, also scavenger test was conducted to ascertain the reactive agent along with the degradation pathway was confirmed by LCMS. Elemental content was also established by using inductively coupled plasma mass spectrometry (ICP-MS). For estimating energy storage capacity cyclic voltammetry (CV) was performed. It was observed Bi2MoO6/MXene nanostructured composite electrodes had specific capacitance of 642.91Fg− 1, power density of 1.24 kWkg− 1, and energy density of 22.32 Whkg− 1 at a current density of 5Ag− 1 also it exhibited 64.42% capacity retention having current density 20 Ag− 1 throughout 10,000 Galvanostatic charge discharge (GCD) cycles. High electrical conductivity of Bi2MoO6/MXene electrode was again examined by Electrochemical impedance spectroscopy (EIS). These findings demonstrate the potential of Bi2MoO6/MXene nanostructured composites in both photodegradation and energy storage applications.

High‐Performance Alkaline Battery‐Supercapacitor Hybrid Based on Bimetallic Phosphide/Phosphate

AbstractTransition metal‐based materials explored for energy storage applications viz. batteries, supercapacitors and more recently battery‐supercapacitor hybrids (BSHs) abundantly involve Co‐based materials. However, the supply chain issues and low electronic conductivity force us to look for alternative options. In this regard, Co‐free binary metal phosphide/phosphate consisting of Ni and V metal (NiVP/Pi) microspheres as the positive electrode of BSH which shows a high specific capacity of 502 C g−1 (1004 F g−1) at 2 mV s−1 while retaining a high specific capacity of 214 C g−1 (428 F g−1) at 12 A g−1 is reported. The high electronic conductivity of binary metal phosphide in NiVP/Pi electrode and the rich electrochemical active sites due to Ni and V metal centres results in exciting performance. More interestingly, the hybrid device is successfully developed by employing NiVP/Pi as the positive electrode and carbon nanotubes (CNTs) as the negative electrode. The hybrid device (NiVP/Pi//CNT) is able to achieve a maximum energy density of 22.17 Wh kg−1 and a power density of 5 kW kg−1 with 91.7% capacitance retention after 7500 continuous galvanostatic charge–discharge cycles.

Enhanced Specific Capacitance and Cycling Stability of Li2Cu2(MoO4)3 of NASICON Family of Supercapacitor Applications

AbstractNASICON electrode materials exhibit a broad spectrum of electrochemical potentials, robust ionic conductivity, and structural and thermal stabilities. Using solid state reaction method, Li2Cu2(MoO4)3 was synthesized, a member of NASICON family of compounds based on molybdenum. Various analytical techniques employed to assess structural and morphological properties of synthesized nanomaterial. X‐ray diffraction (XRD) pattern indicated that generated Li2Cu2(MoO4)3 nanomaterial exhibited orthorhombic crystalline structure, with crystallite size of approximately 48 nm. The nanomaterial morphology was evaluated using field emission scanning electron microscopy (FESEM), showing columnar‐ or fiber‐like morphology composed of some conductivity points. The elemental composition of Li2Cu2(MoO4)3 was analyzed by EDAX analysis, confirming the presence of elements lithium, copper, molybdenum, and oxygen. The optical properties and band gap of Li2Cu2(MoO4)3 were analyzed by ultraviolet visible diffuse reflectance spectroscopy (UVDRS). Elemental composition of surface along with electronic states and oxidation states of component present in the nanomaterial Li2Cu2(MoO4)3 were investigated from X‐ray photoelectron spectroscopy (XPS). Electrochemical evaluation using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopic (EIS) showed a specific capacitance of 250 F g−1 at 3.5 A g−1 with the high retention rate of 95.82% after 3000 cycles, indicating its potential for high performance supercapacitors.

Impact of ultrasonic treatment duration on the microstructure and electrochemical performance of NiZnCo2O4 electrode materials for supercapacitors

This work investigates the impact of different ultrasonic treatment durations on the synthesis and electrochemical performance of NiZnCo2O4 (NZC) supercapacitor electrodes. Optimizing treatment to 20 min resulted in a uniform, compact NiZnCo2O4 layer with improved nanostructures, which increased the surface area and active sites for electrochemical reactions. X-ray diffraction (XRD) confirmed successful NiZnCo2O4 synthesis, revealing distinct crystalline phases of NiO, ZnCo2O4, and Co3O4, with improved crystallinity. Electrochemical tests, conducted using a 1.0 M KOH electrolyte, demonstrated that the NZC-2 electrode treated for 20 min achieved the highest 5.678 F/cm3 volumetric capacitance at 0.5 mA/cm2 current density along with 70.5 Wh/kg an energy density at 260 W/kg power density. The galvanostatic charge-discharge and cyclic voltammetry tests revealed that NZC-2 maintained superior charge-discharge efficiency, showing the longest discharge time at 1 mA/cm². Electrochemical impedance spectroscopy (EIS) measurements demonstrated that NZC-2 exhibited the lowest total impedance, thereby enhancing ion transport efficiency. The NZC-2/AC asymmetric supercapacitor showed excellent long-term stability, retaining 64.2% of its capacity after 20,000 charge-discharge cycles. It successfully powered a 1.2 V small fan, demonstrating its practical applicability. The results highlight the crucial importance of ultrasonic treatment in greatly improving the structural and electrochemical characteristics of NiZnCo2O4 electrodes, which opens up possibilities for the advancement of high-performance supercapacitors.

Highly efficient β-Bi2O3/Bi battery electrodes by reactive annealing from sol-gel precursors

The need of achieving low-impact and low-cost functional materials through sustainable and efficient methodologies is one of the goals of the current research in the field of materials science and energy storage. In this study, a new facile route for obtaining battery-like electrode Bi-based films is presented. Specifically, ~1.3 μm-thick β-Bi2O3 films were prepared from oxynitrate via a simple sol-gel/elution process upon titanium foils, followed by annealing in forming gas at 350°C. A multi-technique approach, involving Raman, X-ray Photoelectron Spectroscopy, X-ray Diffraction, Scanning Electron Microscopy and optical characterization, demonstrates the formation of a nanocrystalline porous bismuth oxide (20-30nm in size) consisting of β-Bi2O3 phase with the crucial presence of Bi0. Annealing at 350°C in different environments (i.e. air and N2), do not produce crystalline phases.The reported method improves the synthesis of β-Bi2O3 phase through a ~1μm-thick film realization and a controlled phase production by reactive annealing at moderate temperatures.Cyclic Voltammetry and Galvanostatic Charge Discharge analyses reveal a double-redox behaviour for the β-Bi2O3 /Bi0 battery electrode with a specific capacity (capacitance) of 195mA*h/g (350F/g) at 0.5A/g. The data highlight the promising usage of sol-gel/elution for the realization of ~1μm-thick film for energy storage applications.

Co3O4/rGO based nanocomposite architectures as electrodes for advanced energy storage and their pseudocapacitive attributes

In response to escalating global challenges in energy storage, this study embarked on captivating exploration of electrochemically proficient Co3O4 composites, seamlessly integrated with varying concentrations of reduced graphene oxide (5 %, 10 %, and 15 %). Using a single-step hydrothermal method, Co3O4 was synthesized, followed by a solvothermal process to produce Co3O4/rGO composites. These composites were then applied to Nickel Foam to fabricate electrodes. The structural properties of these novel Co3O4/rGO/NF electrodes were analyzed using X-ray Diffractometer, which confirmed the distinctive crystalline structure of Co3O4 and indicated no phase transformation after the introduction of rGO. Morphological analysis through a Field Emission Electron Microscope and Transmission Electron Microscope revealed layered structures and increasing porosity correlated with higher rGO concentrations. Electrochemical performance was rigorously tested through cyclic voltammetry, which verified the pseudocapacitive attributes of the samples. Additionally, galvanostatic charge-discharge studies highlighted that the electrode containing 15 % rGO demonstrated highest (Cs = 1360 Fg−1) at 1.7 Ag−1, with 86 % of cyclic retention after 5000 cycles. Electrochemical impedance spectroscopy further demonstrated superior conductivity, underscoring the potential of these electrodes'for supercapacitor applications.

Porous activated carbon electrodes derived from Eleusine coracana biowaste in electric double layer capacitors: Nanoarchitectonics and performance

The development of high-performance supercapacitors from biowaste is crucial for advancing sustainable and renewable energy storage technologies. In this study, we report the fabrication of electrodes for high-performance supercapacitors using porous carbon derived from red millet (Eleusine coracana) straw. Porous carbon was synthesized via a two-step chemical activation process using KOH, resulting in a hierarchical pore structure comprising macro-, meso-, and micropores. The red millet-based porous carbon electrodes, assembled in a two-electrode symmetrical supercapacitor, exhibited a specific capacitance of 68 Fg⁻1 at a current density of 0.5 Ag⁻1 in a 1 M Na₂SO₄ aqueous electrolyte. At a mass loading of 5 mg per electrode, the system demonstrated a specific capacitance of 300 Fg⁻1 at 1 Ag⁻1, with an energy density of 9.1 Whkg⁻1 and a power density of 1.86 kWkg⁻1, as determined from galvanostatic charge-discharge measurements. Additionally, the supercapacitor showed excellent cyclic stability, retaining 98.78% of its initial capacitance after 5000 cycles at 10 Ag⁻1. These findings highlight the potential of porous carbon derived from agricultural biowaste for scalable applications in electric double-layer capacitors.

Y-Shaped Acceptor-π-Donor-π-Acceptor Configured Anthraquinone-Tethered Phenothiazine Molecular Scaffold for High-Performance Organic Pseudocapacitors.

For the first time acceptor-π-donor-π-acceptor (A-π-D-π-A) based Y-type organic electrode material have been designed and successfully utilized in supercapacitor (SC) application. This Y-type molecular architecture coined as AQ-Im-PTZ-Im-AQ based on anthraquinone (AQ) (A)-imidazole (Im) (π)-phenothiazine (PTZ) (D)-imidazole (Im) (π)-anthraquinone (AQ) (A) in combination with graphite foil (GF). As-fabricated PTZ-Im-AQ/GF and AQ-Im-PTZ-Im-AQ/GF electrode have shown the good energy storage properties in three-electrode supercapacitor system. Moreover, two-electrode symmetric supercapacitor (SSC) device based on AQ-Im-PTZ-Im-AQ/GF electrode exhibited specific capacitance (Csp) of 68.97 F g-1 at 1 A g-1 current density. The specific electron density (ED) of SSC was observed to be 12.06 Wh kg-1 at a specific power density (PD) of 1798.50 W kg-1. The SSC device exhibited 81.62 % of Csp retention after 5000 galvanostatic charge-discharge (GCD) cycles. For real world applications, AQ-Im-PTZ-Im-AQ/GF electrode was tested in symmetric Csp coin cell with applied potential voltage window of -0.4 to 1.0 V was found to be 112.32 F g-1 at 0.5 A g-1. Moreover, it realized high specific capacitance and high energy density of 19.66 Wh kg-1 at 891.94 W kg-1 power density. As a results, AQ-Im-PTZ-Im-AQ/GF make as an attractive electrode material for application in next-generation SCs.

STUDYING THE ELECTROCHEMICAL PROPERTIES OF POTASSIUM-DOPED SODIUM-MANGANESE OXIDE CATHODE MATERIALS FOR SODIUM-ION BATTERIES

The development of layered sodium manganese oxide cathode materials with high capacity and long life is one of the keys to boosting the performance of sodium-ion batteries (SIBs), but it remains a great challenge. In this work, a potassium doped P2-type sodium manganese oxide, Na0.8K0.1Mn0.9O2 (NKMO), is developed as a high-capacity and long-lasting cathode for high-performance SIBs. Sodium-potassium-manganese oxide Na0.8K0.1Mn0.9O2 was synthesized by a conventional solid-state reaction method. Crystal structure and morphology of the NKMO material were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The NKMO material was utilized to fabricate CR2032-type coin cells, and later evaluated for its electrochemical characteristics. The electrochemical characteristics of NKMO were evaluated through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charging-discharging (GCD) at different current densities on a NEWARE battery testing system. The NKMO material had a superior initial charge and discharge capacity, approximately 130 mAh.g-1 and 125 mAh.g-1, respectively, within the voltage range of 1.5-4 V at a current density of 0.1 C. Remarkably, the capacity remained stable at 100 mAh.g-1 even after 100 cycles. These findings indicate that NKMO is a highly promising cathode material for sodium-ion batteries.

Novel Ball-Type Phthalocyanines with Eight Benzotriazole Groups: Synthesis, Computational DFT Studies, and Supercapacitor Properties

Abstract Novel four MBTOB-bridged ball-type metallophthalocyanines were obtained from 4, 4'-((methylenebis(6-(2H-benzo[d][1, 2, 3]triazol-2-yl)-4-(2, 4, 4-trimethylpentan-2-yl)-2, 1-phenylene))bis(oxy))diphthalonitrile by means of transition metal (II) acetate salts in 2-dimethylaminoethanol. The new starting bisphthalonitrile compound was accomplished from 2,2'-methylenebis[6-(benzotriazol-2-yl)-4-tert-octylphenol] and 4-nitrophthalonitrile in dimethylformamide under the catalysis of potassium carbonate at 50○C. The structural characterization of the compounds was accomplished by infrared, proton-nuclear magnetic resonance, matrix-assisted laser desorption/ionisation time-of-flight mass, and ultraviolet–visible spectroscopic methods. The supercapacitor performances of the electrodes were examined by cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy analyses. The specific capacitances obtained from the GCD measurements were calculated as 320.4 ± 15.1 F/g for ball-type zinc (II) phthalocyanine in three electrode systems. The highest specific capacitance value was found in the electrode containing ball-type nickel (II) phthalocyanine as 929.8 ± 32.8 F/g at a scan rate of 100 mV/s. In symmetric supercapacitor measurements, the capacitance retention value was 100.7% after 5000 cycles.

Polyoxometalate/α-Fe2O3/polyaniline composite: Tailored approaches for high-performance supercapacitors

The need for portable, high-performance electronics that have high power or energy density has increased significantly in recent years. In this work, a composite material was coated on stainless steel that consists of polyoxometalate (POM)/α-Fe2O3/polyaniline (PANI) as an electrode material for a symmetric supercapacitor. α-Fe2O3 was prepared using starch as a template while PANI was electrodeposited. The physical and chemical characteristics of the modified electrodes were investigated via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electrochemical techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic chargedischarge (GCD) experiments. In 1 M H2SO4, the composite had a specific capacitance of 528 F/g at a current density of 0.2 A/g. In addition, the composite exhibited a high energy density of 73.4 Wh kg−1 at a high-power density of 7.14 kW kg−1 and 91.62 % capacity retention after 10 cycles. The results show that POM/α-Fe2O3/PANI is a promising composite electrode for use as a supercapacitor electrode material.

Zinc cobalt sulfide with carbon (graphene oxide and CNT) based nanocomposite as positive electrode for asymmetric coin cell supercapacitors

Abstract The world dependence on portable electronic devices has increased the demand for high-performance energy storage devices. The use of transition metal sulfides as faradaic electrode materials for electrochemical energy storage is rapidly increasing due to their high energy density. Herein Zinc Cobalt Sulfide (ZCS) with graphene oxide (GO) and carbon nanotubes (CNT) were used to create an interconnected ZCS composite network using a solvothermal technique. The materials were characterized by utilizing XRD, FT-Raman, TGA, FESEM/EDX, XPS, and BET. The electrochemical performance of the materials was examined using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The prepared electrodes exhibited both pseudocapacitor behavior and double-layer capacitor behavior, indicating the hybrid nature. Furthermore, All the electrode ZCS, ZCS/GO, ZCS/CNT, and ZCS/GO/CNT electrodes demonstrated higher capacitance behavior, with values of 420, 551, 585 and 811 F g−1 at 1 A/g. Among these ZCS/GO/CNT electrode exhibits outstanding electrochemical properties, with a notable retention of 81.08% at 10 Ag−1 because Combining ZCS nanoparticles with interconnected GO and CNT provides excellent electronic conductivity and stability. The assembled ZCS/GO/CNT//graphene oxide asymmetric coin cell (ACC) supercapacitor showed a high energy density of 33.3 Wh kg–1 at a power density of 624 W kg–1. The 3D nanostructure of ZCS/GO/CNT/Graphene oxide has great potential for developing foldable energy storage devices.

Unravelling the effect of crystal lattice compression on the supercapacitive performance of hydrothermally grown nanostructured hollandite α-MnO2 induced by incremental growth time

Manganese oxide (α-MnO2) nanoparticles are highly recognised for their use in supercapacitor applications. This study demonstrates the successful synthesis of flower-like and nanorods hollandite α-MnO2 by a simple one-pot hydrothermal technique at various reaction times. The synthesised nanoparticles were characterised by various physicochemical and electrochemical characterisation techniques. The influence of the various reaction times on the structural and morphological properties was evaluated by X-ray diffraction (XRD) and scanning electron microscope. XRD patterns revealed that the synthesized MnO2 nanoparticles are tetragonal structures with crystallite sizes ranging from 13.69 to 20.37 nm estimated from the Williamson–Hall method. Moreover, the functional groups and surface area were examined by Fourier transform infrared spectroscopy and Bruner–Emmert–Teller, respectively. Furthermore, the compositional elements were studied by X-ray photoemission spectroscopy and energy-dispersive X-ray spectroscopy. Finally, the electrochemical performances were studied using cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The GCD characteristics revealed that the optimised α-MnO2 has a good capacitive behaviour, which predicts the potential application in energy storage. Electrochemical studies revealed that the 3 h-MnO2 sample exhibited a superior electrochemical behaviour and demonstrated a high specific capacitance of 132 F/g at a current density of 1A/g.

Supercapacitor performance of pure and Ni-doped CuO electrodes prepared by USP

Abstract In this study, the ultrasonic spray pyrolysis (USP) technique was employed to fabricate pure and 3% Ni-doped copper oxide (CuO) thin films (TFs) on In2O3/SnO2 (ITO) coated glass substrates. X-ray diffraction (XRD) analysis revealed that both pure and 3% Ni-doped CuO TFs exhibit a polycrystalline structure with the tenorite phase oriented preferentially along the (111) plane. The morphological properties of these TFs were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging. Energy dispersive x-ray spectroscopy (EDX) confirmed that the deposited TFs achieved the desired stoichiometry. The electrochemical properties of both pure and 3% Ni-doped CuO TFs were evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). At a current density of 1 A g−1, the specific capacitance of pure CuO TFs was found to be 78 F g−1, decreasing to 2 F g−1 at 10 A g−1. In contrast, Ni-doped CuO TFs exhibited a specific capacitance of 722 F g−1 at 1 A g−1 and 20 F g−1 at 10 A g−1. These results indicate that Ni-doping significantly enhances the specific capacitance values. The superior performance of Ni-doped CuO electrodes is attributed to their uniformly high porosity and improved electrical conductivity, demonstrating Ni-doped CuO as an optimal electrode material for pseudocapacitors.

Characterization of green-synthesized carbon quantum dots from spent coffee grounds for EDLC electrode applications

This study investigates the green synthesis of carbon quantum dots (CQDs) from spent coffee grounds using a hydrothermal method, offering an eco-friendly, cost-effective, and straightforward approach to nanomaterial production. The synthesized CQDs, with particle sizes ranging from 1.6 to 4.4 nm, exhibited notable fluorescence, achieving quantum yields of 37.0 %, 54.3 %, and 63.3 % depending on the coffee source. Characterization technique, including XRD, FTIR, SEM, TEM, and BET, confirmed their structural suitability of these CQDs for energy storage applications. Their electrochemical performance was evaluated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Among the CQDs tested, those derived from spent Liberica coffee ground (medium roasted) demonstrated superior performance, with a discharging specific capacitance of 97.5 F/g, an energy density of 4.3 Wh/kg, and a power density of 130.6 W/kg at a current density of 0.5 A/g. Additionally, they exhibited acceptable internal resistance (Ra = 0.01 kΩ and Rab = 16.9 kΩ), indicating favourable charge transfer characteristics. These results underscore the enhanced energy storage potential of CQDs derived from spent coffee grounds. The findings not only highlight the excellent electrochemical performance but also support the viability of biomass waste as a valuable resource for advanced energy storage applications, promoting sustainable, eco-friendly technologies.

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.

Flexible Supercapacitor Device Based on Laser‐Synthesized Nanographene for Low‐Power Applications

Laser‐induced graphene (LIG) and laser‐induced reduced graphene oxide (LIrGO) are two relatively recent graphene‐based nanoscale materials suitable for miniaturized flexible supercapacitors. This study employs direct laser engraving techniques to generate patterns on flexible substrates, such as paper and polyamide (PI). This methodology allows fine control over the formed nanographene structures to fabricated LIG and LIrGO supercapacitors. The LIG on PI exhibits a distinctive porous structure and high surface area, adsorption, and transportation of ions. Furthermore, paper‐based LIrGO electrodes are recyclable and are formed in a single step. The morphological study is done using scanning electron microscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. Galvanostatic charge–discharge studies at 0.05 mA cm−2 current density show an areal capacitance of 3.69 mF cm−2 for LIG and 1.61 mF cm−2 for LIrGO. The comparable energy densities for LIG and LIrGO are 0.32 and 0.16 μWh cm−2, respectively. From the calculative analysis of both types, the variation in specific areal capacitance enabling effective is 56.3% from GCD, indicating that the LIG device performs better. Finally, a portable potentiostat is employed to investigate the viability of utilizing supercapacitors to operate self‐powered sensors in a portable and integrable fashion.

Constructing Co3O4 Nanowire@NiCo2O4 Nanosheet Hierarchical Array as Electrode Material for High-Performance Supercapacitor.

The Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array was constructed on Ni foam using hydrothermal and annealing approaches in turn, from which a NiCo2O4 nanosheet could self-assemble on the Co3O4 nanowire. The structure and morphology of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array were characterized via XRD, EDS, SEM, and FESEM, respectively. The electrochemical performance of the composite array was measured via a cyclic voltammetry curve, galvanostatic current charge-discharge, charge-discharge cycle, and electrochemical impedance and then compared with the Co3O4 nanowire. The results show that the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could reach a high value of 2034 F g-1 at a current density of 2.5 A g-1. After 5000 galvanostatic charge-discharge cycles, the specific capacitance of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could still maintain 94.7% of the original value. Therefore, the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array would be a desirable electrode material for a high-performance supercapacitor.