Galvanostatic Charge Discharge Research Articles

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.

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.

Electrochemical boost via thermally reduced graphene oxide for tailoring composite paste electrodes

Carbon-based composite materials are employed in diverse electrochemical applications, such as in catalysis, (bio)molecular sensing, and energy storage. In practice, electrode material needs to be highly conductive to allow high-speed electron transference to electrolyte species and possess high-surface area to obtain greater measured signals and power capabilities, as well as long useful life and stability. In this sense, graphene derivatives emerge as interesting candidates, even more so if they constitute part of practical, economical and versatile paste electrodes.This work presents a detailed analysis of the electrochemical performance of paste electrodes fabricated with multilayer partially reduced graphene oxide (rGO). The rGO was strategically produced via thermal treatment as a key factor that minimizes both mass loss and energy consumption. The results obtained through diffraction, microscopy and spectroscopy techniques show an effective partial reduction in the range of 100 to 400 °C. Furthermore, the enhanced electrochemical performance of rGO was determined by exploring the specific capacitance from cyclic voltammetry (CV) and galvanostatic charge–discharge measurements (GCD) as well as charge transfer resistance via electrochemical impedance spectroscopy (EIS). Our results evidence how an integral performance with suitable chemical, structural and morphological properties achieved for GO heat-treated at 200 °C leads to an improved electronic conductivity when a small part is combined with graphite in paste electrodes. This latter combination provides higher versatility compared to other alternatives since it arises as an economical and effective carbonaceous matrix for (bio)electrochemical sensors, hybrid supercapacitors or other desired nanotechnological applications.

Sustainable pseudocapacitance potential of a hybrid triad involving activated carbon derived from polyester wastes

This study introduces an innovative approach to fabricate high-efficiency supercapacitor electrodes by utilizing waste polyester (PES), a common fabric waste, as a precursor for producing activated carbon. This approach not only addresses waste disposal issues but also provides a valuable resource for various environmental and industrial applications. Through a series of chemical and thermal treatments, PES waste is transformed into a porous carbon structure, which is then functionalized with PPy and V2O5 to enhance its electrical conductivity and electrochemical performance. The synthesized composite is characterized by several analytical and spectral techniques to elucidate the morphological, structural and surface properties. The specific surface area of the hybrid composite material is 50.4 m2g−1. Cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy are employed to evaluate the performance of the composites as supercapacitor electrodes. From the CV curves, the electrochemically active surface area was calculated to be 0.085 m2g-1. The composite exhibits a remarkable specific capacitance of 535 Fg-1 and energy as well as power density values of 171 W h Kg−1 and 2877 W Kg−1 respectively at a current density of 2 Ag−1. The material was fabricated into device and was observed to show excellent cycling satbility for up to 10,000 cycles.

Electrochemical performance of cobalt-doped NiO thin films synthesized by spray pyrolysis

ABSTRACT In this work, various cobalt-doped NiO thin films have been synthesized via the spray pyrolysis. The cobalt-doped NiO thin films show a cubic phase with preferred orientation along the (111) plane. The scanning electron microscopy images of the cobalt-doped NiO thin films show interconnected flakes with small agglomerated particles. The optical bandgap decreases from 3.30 eV for the undoped NiO thin film to 2.90 eV for 20 mol% cobalt doping, with an increase in cobalt doping concentration in NiO. The electrochemical activities have been tested in 2M KOH electrolyte with cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The highest specific capacitance observed for the 10 mol% cobalt-doped NiO thin film electrode is 760 Fg−1 at a scan rate of 5 mVs−1. The 10 mol% cobalt-doped NiO thin film electrode shows 92% retention in capacitance after 1000 cycles and a low charge transfer resistance of 10 Ωcm2.

NiCo-MOFs derived carbon matrix composites: A promising electrode construction for high-performance supercapacitors

Metal-organic frameworks (MOFs) are great precursors and templates for preparing adsorbents, catalysts and electrodes due to the porous structure and high specific surface area. We report a promising approach to prepare nanocrystalline Co, Ni sulfides (CNS) embedded and N self-doped porous carbon (NPC) matrix composites derived from NiCo-MOFs. The CNS@NPC composite was investigated as electrodes for hybrid supercapacitors (HSCs). The prepared electrode achieved specific capacitance of 2789 F g−1 at 1 A/g, and high capacitance retention of 88.93% after 6000 galvanostatic charge–discharge (GCD) cycles under 10 A/g. The HSC structured with CNS@NPC//AC achieved an energy density of 46.79 Wh kg−1 at power density of 800 W kg−1. Meanwhile, specific capacitance of 131.56 F g−1 at 1 A/g and capacitance retention of 99.17% over 6000 GCD cycles under 3 A/g were obtained. Space confinement by the carbon skeleton effectively prevents the aggregation of the redox active nanocrystalline and improves the durability of the electrode. Meanwhile, the carbon skeleton provides abundant charge transfer channels to enhance the redox reaction. In other words, synergistic effect of the carbon skeleton and the active redox nanocrystalline significantly improves the electrochemical properties of the composite.

Silver-Doped Reduced Graphene Oxide/PANI-DBSA-PLA Composite 3D-Printed Supercapacitors.

This study presents a novel approach to the development of high-performance supercapacitors through 3D printing technology. We synthesized a composite material consisting of silver-doped reduced graphene oxide (rGO) and dodecylbenzenesulfonic acid (DBSA)-doped polyaniline (PANI), which was further blended with polylactic acid (PLA) for additive manufacturing. The composite was extruded into filaments and printed into circular disc electrodes using fused deposition modeling (FDM). These electrodes were assembled into symmetric supercapacitor devices with a solid-state electrolyte. Electrochemical characterization, including cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests, demonstrated considerable mass-specific capacitance values of 136.2 F/g and 133 F/g at 20 mV/s and 1 A/g, respectively. The devices showed excellent stability, retaining 91% of their initial capacitance after 5000 cycles. The incorporation of silver nanoparticles enhanced the conductivity of rGO, while PANI-DBSA improved electrochemical stability and performance. This study highlights the potential of combining advanced materials with 3D printing to optimize energy storage devices, offering a significant advancement over traditional manufacturing methods.

Bio-Inspired Self-Healing Silicon Anodes: Harnessing Tea Polyphenols to Enhance Lithium-Ion Battery Performance.

This study introduces an anode material for lithium-ion batteries, achieved by integrating tea polyphenols (TP) with the widely utilized polyacrylic acid (PAA) binder. The composite material capitalizes on the intrinsic self-healing properties of TP, enhancing the anode's durability and adhesiveness without the need for additional organic synthesis. The incorporation of TP has been demonstrated to significantly elevate ionic conductivity and expedite lithium ion diffusion, thereby reducing interfacial resistance and decelerating the rate of capacity fade due to electrolyte decomposition and silicon particle expansion. Employing a comprehensive analytical toolkit, including Fourier transform infrared spectroscopy, thermogravimetric analysis, peel strength measurements, and density functional theory calculations, we elucidated the physicochemical properties of the Si@PAA-TP anode. The anode's electrochemical performance was systematically assessed through galvanostatic charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy, with scanning electron microscopy providing insights into postcycling mechanical property alterations. This research advances a cost-effective, high-performance adhesive strategy for silicon anodes and contributes to the development.

NiO/MnO2coated on carbon felt as an electrode material for supercapacitor applications.

Transition metal oxides have demonstrated excellent capability for charge storage when used in supercapacitor electrodes. This study undertook the hydrothermal synthesis of bimetallic nickel and manganese oxide (NiO/MnO2) on a carbon-felt (CF) substrate. NiO/MnO2/CF electrode was characterized and examined in a three-electrode system in a potassium hydroxide electrolyte. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge analyses revealed Faradaic behavior during charge storage, a specific capacity of 1627 F/g, and a stability of 96.8% after 5000 consecutive charge-discharge cycles. Subsequent investigations were conducted in a two-electrode system for constructing a symmetrical supercapacitor using the NiO/MnO2/CF electrode. The energy and power densities were determined as 43Wh/kg and 559 W/kg. Additionally, the stability of the constructed supercapacitor device was examined over 5000 consecutive cycles, verifying a 92% stability through charge-discharge cycles. Finally, the fabricated supercapacitor was utilized to power an LED lamp, successfully maintaining the illumination for 53 seconds.&#xD.

Solid-state synthesis of nickel selenide for high-performance supercapacitors

This study focuses on the synthesis and electrochemical characterization of nickel diselenide (NiSe2) as a promising electrode material for supercapacitors. NiSe2 was synthesized through a facile solid-state process involving the mixing of nickel acetylacetonate and selenous acid, followed by drying and sintering at 500 °C under inert conditions. The resulting NiSe2 exhibited a granular structure with worm-like surface architecture and particle size ranging from 20 to 100 nm. The electrochemical performance of NiSe2 was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a 6 M KOH electrolyte. NiSe2 demonstrated a high specific capacitance of 744.7 F g−1 at a discharge rate of 1 A g−1, with an outstanding rate capability retaining the capacitance of 483.6 F g−1 at 10 A g−1, and exceptional long-term cycling stability. The kinetic analysis revealed that the energy storage mechanism in NiSe2 primarily involves diffusion-controlled charge storage. EIS further confirmed the favorable charge transfer properties of the NiSe2 electrode. Overall, NiSe2 synthesized via the proposed method shows great promise for application in high-performance supercapacitors.

Catalytic and Electrochemical Study of Cu-ZSM-5/MCM-41.

Hierarchically structured micro-mesoporous ZSM-5/MCM-41 composite materials incorporating copper ions were synthesized using pre-synthesized ZSM-5 and cetyltrimethylammonium bromide (CTAB) as a template for forming the MCM-41 structure. The composites were characterized through powder X-ray diffraction, N2 adsorption-desorption, diffuse reflectance spectroscopy (UV-vis DRS), Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and energy dispersive X-ray spectroscopy. X-ray diffraction confirmed well-ordered ZSM-5 and MCM-41 structures, and UV-vis DRS showed successful copper ion incorporation. N2 adsorption-desorption revealed the presence of both microporous and mesoporous structures. To evaluate their catalytic performance, Cu-incorporated ZSM-5/MCM-41 composite catalysts were assessed through the oxidation reaction of ethylbenzene using tert-butyl hydroperoxide (TBHP) as the oxidizing agent. With a 9% (w/w) Cu-ZM-5 (5 wt % copper-incorporated ZSM-5/MCM-41) catalyst and an oxidant to ethylbenzene molar ratio of 2:1 at 40 °C in the absence of a solvent for 4 h, the process yielded acetophenone (93.2%) as the major product. Additionally, these Cu-incorporated composites were examined as electrode materials for electrochemical storage. Cyclic voltammetry and galvanostatic charge-discharge studies showed that Cu-ZM-5 exhibited pseudocapacitive behavior, with a capacitance of up to 366 F g-1 at a current density of 1 A g-1, surpassing ZSM-5 and ZSM-5/MCM-41. These results highlight Cu-ZM-5's potential as an effective electrode material for electrochemical storage applications like supercapacitors.

Cellulose acetate-based polymer electrolyte for energy storage application with the influence of BaTiO3 nanofillers on the electrochemical properties: A progression in biopolymer-EDLC technology

The bio-based solid polymer electrolyte serves as a promising choice for the next generation of energy storage devices to meet the requirement of green chemistry. In the current research, a green plasticized magnesium ion-conducting biopolymer electrolyte was developed using simple solution casting method for Electric Double Layer Capacitors (EDLC) applications. The biopolymer Cellulose Acetate (CA) as the host polymer, with varying concentrations of BaTiO3 as the nanofiller, Mg(CF3SO3)2 as the ionic dopant, and PEG as the plasticizer. A 2 wt% addition of BaTiO3 to the biopolymer electrolyte exhibits maximum conductivity measuring 2.4 × 10−3 S/cm. Linear Sweep Voltammetry (LSV) analysis demonstrates maximum stability voltage of 3.51 V. The ionic transference number (tion) and (tMg2+) were determined to be 0.99 and 0.41 respectively. The fabricated EDLC device with the same electrolyte showed polarisation curve without any noticeable peaks in the Cyclic Voltammetry (CV) plot, indicating no redox reactions occurring at the electrode-electrolyte interface. Galvanostatic Charge Discharge (GCD) results showed excellent coulombic efficiency, stability and Energy Density and Power Density performance over 2000 cycles. The incorporation of BaTiO3 into biopolymer membranes presents a viable approach towards sustainable energy storage solutions by enhancing the energy storage capacity of EDLC devices.

Synthesis of Carbon Nanofibers from Lignin Using Nickel for Supercapacitor Applications

Carbon fiber is known for being lightweight and adaptable, making it useful for various current and future applications. However, to broaden the use of carbon fibers beyond niche applications, production costs must be lowered. A potential approach to achieving this is by using more affordable raw materials, such as lignin, which is renewable, cost-effective, and widely available compared with the materials commonly used in industry today. This study explores the impact of metal ions on the quality of carbon fiber derived from lignin, focusing on its mechanical and electrochemical properties and morphology. The effect of a specific metal ion (Ni(NO3)2·6H2O) was examined by incorporating it into the spinning solution. The carbonization stage of the fiber was conducted at temperatures of 800, 900, and 1000 °C in an inert atmosphere. Scanning electron microscopy (SEM) analysis showed no defects or damage in any of the fibers. Therefore, it was concluded that moderate concentrations of Ni2+ ions in the fibers do not influence the stabilization or carbonization processes, thus leaving the mechanical properties of the final carbon fiber unchanged. These carbon nanofibers were also tested as a sustainable alternative to the non-renewable materials used in electrodes for energy storage and conversion devices, such as supercapacitors. Electrochemical performance was assessed in a 6 M KOH solution using a two-electrode cell configuration. Galvanostatic charge–discharge tests were performed at different current densities (0.1, 0.25, 0.5, 1.0, and 2.0 A g−1). The specific capacitance of the carbon nanofibers was determined from CVA data at various scan rates: 5, 10, 20, 40, 80, and 160 mV s−1. The results indicated that at 0.1 A g−1, the capacitance reached 108 F g−1, and at a scan rate of 5 mV s−1, it was 91 F g−1. The innovation of this work lies in its use of lignin, a renewable and widely available material, to produce carbon fibers, reducing costs compared with traditional methods. Additionally, the incorporation of nickel ions enhances the electrochemical properties of the fibers for supercapacitor applications without compromising their mechanical performance.

Insights into the electrochemical performance of manganese dioxide coated metallic foils as potential electrodes for supercapacitors

AbstractManganese dioxide (MnO2) is a promising electrode material for supercapacitors due to its high theoretical specific capacitance. In this study, MnO2 particles were synthesized using a simple hydrothermal method and subsequently coated onto silver, nickel, and aluminum foils via dip coating. The structural, morphological, and functional properties of the resulting MnO2 nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT–IR). Electrochemical impedance spectroscopy (EIS), galvanostatic charge–discharge (GCD), and cyclic voltammetry (CV) were employed to investigate the electrochemical performance of the coated metallic foils. The results demonstrated that MnO2/Ag foils exhibited the highest specific capacitance of 198 F g–1 at a scan rate of 0.25 A g−1, accompanied by excellent cycle stability (89% capacitance retention). This performance surpassed that of MnO2/Ni and MnO2/Al foils, which exhibited maximum specific capacitances of 150 and 101 F g−1, respectively. Additionally, MnO2/Ag foils displayed the highest charge storage capacity, as evidenced by EIS analysis, reaching 4000 Ω, nearly double that of MnO2/Ni and MnO2/Al foils. These findings highlight the potential of cost-effective and high-performance MnO2/Ag foils for widespread applications in energy storage devices such as electrochemical capacitors. Graphical Abstract

Innovative Nanoarchitectures: CuO:Er2O3 Synergy for Enhanced Performance in Energy Storage and Generation Applications

ABSTRACTIn this study, we have synthesized facile Cu‐based CuO:Er2O3 nanoelectrode material for energy storage and generation. CuO:Er2O3 nanomaterial was synthesized employing phyto‐extract of Amaranthus viridis L. (AVL) as stabilizing and reducing agents. Spherical‐shaped CuO:Er2O3 nanomaterial was initially employed to study supercapacitor behavior. The specific capacitance of 82.25 F/g was found at 0.5 A/g by galvanostatic charge–discharge, whereas the value of 319 F/g was achieved at 2 mV/s by cyclic voltammetry (CV) measurements. Furthermore, CuO:Er2O3 electrode was investigated for water splitting energy generation potential and revealed an overpotential value of 323 mV at 10 mA/cm2 for hydrogen evolution reaction (HER). However, for the oxygen evolution reaction (OER), an overpotential value of 370 mV was found. The electrochemical impedance analysis revealed the faster flow of electrons and ions, suggesting great conductivity and lower resistance of the fabricated electrode. Thus, current electrochemical results are proposing CuO:Er2O3 as an competent electrode for overall energy‐generating as well as storage applications.

Development of new cathode materials for all-iron redox flow batteries using hard carbon-based composites containing niobium pentoxide

We report in this study new cathodes for all-Fe RFBs synthesized using carbon flakes dispersed in plasticizing and hardening agents to obtain hard and dense carbon (HC) materials in the absence and presence (HC-Nb) of niobium pentoxide (Nb2O5). These cathode materials exhibited excellent resistance to wear in acidic solutions and larger potential intervals for water stability (e.g., 1200–1300 mV) compared to conventional graphite (e.g., 800 mV). These characteristics decreased the parasitic occurrence of hydrogen evolution reaction (HER) using a laboratory-made battery cell during the charging process. The latter was based on the Fe0/Fe2+ and Fe2+/Fe3+ redox couples present in the anode and cathode compartments, respectively. The different ex-situ and in-situ characterization studies evidenced that the presence of Nb2O5 in HCs substantially changed their physicochemical properties. The highest heterogenous kinetic rate constant (k0) representing the electrocatalytic activity for electron transfer was verified for the cathode containing 10 wt.% Nb2O5. An electromotive force (EMF) of 1.053 V was verified for the fully charged all-Fe RFB. Galvanostatic charge–discharge (GCD) studies revealed excellent coulombic efficiency (> 88 %) after 300 cycles. A pH control by acid addition as a function of the battery operation is necessary to avoid iron hydroxide formation on the anode’s surface.