Supercapacitive Behavior Research Articles

Zr-MOF composites with zipped and unzipped carbon nanotubes for high-performance electrochemical supercapacitors.

Metal-organic frameworks (MOFs) have gained considerable interest as crystalline porous materials with notable characteristics, such as high surface area and excellent electrochemical performance, particularly in supercapacitor applications. The combination of MOFs with various nanocarbon materials further enhances their performance. This study investigated the combination of zirconium-based MOFs (Zr-MOFs) with graphene oxide nanoribbons (GONRs), zipped carbon nanotubes, and functionalized carbon nanotubes (FCNTs) to fabricate composites with elevated electrical conductivity, adjustable surface area, chemical robustness, mechanical strength, and customizable attributes for specific applications. Zr-MOFs exhibit remarkable capacitance, making them promising electrode materials for supercapacitors. GONRs and FCNTs have recently emerged as focal materials owing to their unique properties, which make them promising materials for electrochemical energy storage devices. A thorough investigation of the supercapacitive behavior of GONRs, FCNTs, Zr-MOFs, Zr-MOFs/FCNTs, and Zr-MOFs/GONRs in 1 M H2SO4 using different evaluation systems (three- and two-electrode systems) revealed a significant enhancement in the capacitance of Zr-MOFs after the introduction of GONRs and FCNTs. Employing Zr-MOF/GONR and Zr-MOF/FCNT composites as positive electrodes and GONRs as negative electrodes in two-electrode measurements demonstrated remarkable cycling stability by retaining their specific capacitances (Cs) even after 10 000 consecutive charge/discharge cycles at a high current density of 10 A g-1. Moreover, they feature a broad potential window of 1.7 V in the three-electrode system. This extends to 2 V in the two-electrode system, achieving high Cs. This highlights the remarkable electrochemical performance of the Zr-MOF/GONR and Zr-MOF/FCNT composites, offering a compelling approach for energy storage applications.

Supercapacitive behavior of two-dimensional carbon nanosheets with oxygen-induced interfacial modification

Biomass-derived carbon typically contains abundant heteroatomic defects and interfacial functional groups, which can contribute to additional pseudocapacitance. However, the type of interfacial functional groups in biomass-derived carbon is uncontrollable and variable, reducing their homogeneity. In this work, recyclable boric acid was employed as an activator to convert bioaerogels into carbon nanosheets. Subsequently, low-temperature air oxidation was utilized to modulate their thickness and microstructure. Notably, the multiple and uncontrollable functional groups at the carbon interface were uniformly transformed into oxygen-containing functional groups under oxygen induction, resulting in 2D carbon nanosheet materials with enhanced stability properties. Meanwhile, the introduction of more oxygen-containing functional groups, such as carbonyl (C=O) and carboxyl (-COOH) groups, improves material wettability and capacitive properties. In addition, the boron and nitrogen elements doping introduced by activators and precursors enhances its pseudocapacitive properties and electrical conductivity from the carbon lattice perspective. Moreover, the rich electron/deficient effect of BN valence bond can effectively boost their conductivity and rate performance. In fact, the materials present good capacitive properties (high specific capacitance of 298.5 F g−1 in KOH three-electrode system) and CDI (capacitive deionization) performance (good desalting capacity of 35.2 mg g−1 in CDI system).

Cover Picture: Enhancing the Supercapacitive Behaviour of Cobalt Layered Hydroxides by 3D Structuring and Halide Substitution (Batteries & Supercaps 11/2024)

Cover Picture: Enhancing the Supercapacitive Behaviour of Cobalt Layered Hydroxides by 3D Structuring and Halide Substitution (Batteries & Supercaps 11/2024)

Preparation and application of mixed ligand Zn-MOF as electrode materials for supercapacitors applications

In this study, various mixed-linker metal-organic frameworks (MOFs) based on Zn-MOF were successfully synthesized using different ratios of 1,3,5-benzenetricarboxylic acid (BTC) and 1,4-benzenedicarboxylic acid (BDC) as modulator ligands. The characterization results indicated that a lower percentage of BDC ligand effectively enhances the specific surface area of the MOFs while maintaining their microporous structure. Furthermore, the supercapacitive behavior of the synthesized Zn-MOFs with varying mixed ligand ratios was evaluated through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD) measurements in a 6 M KOH electrolyte. Synthesized materials, namely MOF-0 (100 % BTC), MOF-1 (75 % BTC, 25 % BDC), MOF-2 (50 % BTC, 50 % BDC), MOF-3 (25 % BTC, 75 % BDC), and MOF-4 (100 % BDC) were assessed through GCD tests. These tests demonstrated specific capacitance values of 577, 683, 529, 428, and 302 F/g at a current density of 0.5 A/g, respectively. This impressive performance underscores the effectiveness of the mixed-linker strategy in optimizing the electrochemical properties of MOF for energy storage applications.

Effect of γ-rays irradiation on the structural, magnetic, and electrochemical properties of ZnMn2O4 nanoparticles

The study explored the effect of gamma-ray irradiation on the physical, magnetic, and electrochemical properties of ZnMn2O4 synthesized by the burning method. On the physical characterization side, the study utilized multiple metrology techniques to determine the impact of radiation dosage on bond lengths, density, crystallite size, micro strain, lattice constant, and dislocation density. No irradiation impact on the sample's tetragonal spinel structure was observed up to 250 kGy doses. However, the lattice parameters increased post-γ-irradiation and were apparent in the morphology change of irradiated samples compared to control spinel. Conversely, the magnetic parameters decreased post-irradiation based on the vibrating-sample magnetometry (VSM) testing of control and γ-irradiated samples. Changes in parameters like saturation magnetization (Ms) and magneton number (nB) can be attributed to ion-induced disorder and cation distribution in irradiated samples. Finally, the electrochemical testing showed supercapacitor behavior for all ZnMn2O4 samples, with a positive impact of radiation on electrical capacitance and stability. While the γ-irradiated sample with a 250 kGy dose showed a capacitance (Csp) of 515 F/g with 87.6% stability, the control sample had a Csp of 123 F/g and 78% stability. ZnMn2O4 material meets the needs of energy storage devices operating at high ionizing radiation doses.

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.

Supercapacitive behaviors of N/S co-doped biomass porous carbon-based supercapacitors in “water-in-salt” electrolyte

The design of carbon electrode materials and electrolytes is distinct significance for improving the energy density of supercapacitors. Herein, N/S co-doped biomass porous carbon materials based on sustainable resource were prepared by in-situ expansion, heteroatom doping, and subsequent KOH activation strategy by using camellia seed shell as carbon source and ammonium persulfate as dopant and expander. The as-prepared N/S co-doped biomass porous carbon (N/S-CSAC-650) possesses the characteristics of high specific surface area, large pore volume, and suitable heteroatom content. The N/S-CSAC-650 electrode achieves a high specific capacitance of 335.9 F g−1 in the 3 M KOH electrolyte at 0.5 A g−1. The constructed symmetric supercapacitor demonstrates excellent cyclic stability and shows a high retention rate of 98.4 % after 30,000 charge and discharge processes at 2 A g−1. Especially, the energy density of supercapacitors is usually constrained by the narrow electrochemical stability window (ESW) of dilute aqueous solution (1.23 V), in order to effectively widen the ESW of water, herein the “water-in-salt” (WIS) electrolyte strategy is put forward and the ESW of water was extended to 2.94 V by using a 25 M KAc WIS electrolyte. The operating voltage window of the symmetric supercapacitor assembled by 25 M KAc WIS electrolyte and N/S-CSAC-650 electrodes can reach 2.0 V, and a high energy density of 48.86 Wh kg−1 is realized.

Marigold flower-like structured battery-type Cu2O/Co(OH)2 composite electrode material for high-performance supercapacitors

Addressing the limitations of individual Cu2O and Co(OH)2 components, this study aims to develop a high-performance supercapacitor electrode by synergistically combining these materials. A composite electrode material of Cu2O/Co(OH)2 was effectively synthesized on nickel foam via a facile hydrothermal method for supercapacitor applications. The as-fabricated Cu2O/Co(OH)2 composite electrode exhibits a hierarchical marigold flower-like morphology that comprises of many interspersed nanoflakes. This unique morphology offers several advantages, including increased surface area, abundant electroactive sites, and enhanced electrolyte accessibility, all of which contribute to superior electrochemical performance. The Cu2O/Co(OH)2 electrode demonstrates exceptional battery-type supercapacitor behavior, characterized by prominent redox peaks in cyclic voltammetry curves and a well-defined potential plateau during galvanostatic charge-discharge measurements. The electrode delivers an outstanding specific capacitance of 90.21 mA h g⁻1 at a current density of 1.25 A g⁻1 and retains a remarkable 81.91 % capacitance at a high current density of 12.5 A g⁻1. Furthermore, the electrode exhibits impressive cycling stability, maintaining approximately 107.84 % of its initial specific capacity value after 200 cycles at 7.5 A g⁻1. Electrochemical impedance spectroscopy measurements reveal low solution resistance and charge-transfer resistance, signifying efficient charge-transfer kinetics within the electrode. These findings highlight the potential of Cu2O/Co(OH)2 composite electrodes as promising candidates for high-performance supercapacitor applications.

Fullerene C60 functionalized Sm2O3@Eu2O3 bimetallic oxides core shell nanocomposites for zeta potential and energy storage applications

Nanocomposites of Fullerene C60 (FC60) with lanthanide oxides show better energy storage properties compared with any of them alone. In the present research, we have synthesized FC60 (2, 5 and 10 wt%) anchored on Sm2O3@Eu2O3 bimetallic oxides by simple chemical precipitation method. The FC60:Sm2O3@Eu2O3 core shell nanocomposites (NCs) were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), EDX (energy dispersive X-ray), UV–visible, XPS (X-ray photoelectron spectroscopy), and BET (Brunauer–Emmett–Teller) analytical methods. XRD studies revealed mixed phase of monoclinic and orthorhombic crystal structure with irregularly scattered small plate/flake like morphology agglomerated and formed as large grains. Electrochemical supercapacitive behaviour of Sm2O3@Eu2O3 bimetallic oxides showed specific capacitance (SCs) of 665.075F/g in 3 M KOH as electrolyte. The SCs of FC60 (5 wt% and 10 wt%):Sm2O3@Eu2O3 electrode material in 3 M KOH solution was found to be 795.92F/g and 1120F/g at a current density of 1 A/g (scan rate of 10 mV/s). FC60 (10 wt%):Sm2O3@Eu2O3 NCs showed excellent capacitive retention of 90.8 % after 10,000 cycles. The Zeta potential (ζ) studies of FC60:Sm2O3@Eu2O3 NCs showed decrease in the mean Zeta potential (ζ) from 34.23 mV to 11.97 mV with decrease in electrophoretic mobility (2.667 to 0.933 (μm cm/Vs)) attributed to the cationic nature of the FC60:Sm2O3@Eu2O3 NCs. The FC60:Sm2O3@Eu2O3 NCs with high cycle stability and charge density can be a better candidate for high energy storage devices, supercapacitor, dielectric related applications.

Enhancing the Supercapacitive Behaviour of Cobalt Layered Hydroxides by 3D Structuring and Halide Substitution

AbstractAmong the two‐dimensional (2D) materials, layered hydroxides (LHs) stand out due to their chemical versatility, allowing the modulation of physicochemical properties on demand. Specifically, LHs based on earth‐abundant elements represent promising phases as electrode materials for energy storage and conversion. However, these materials exhibit significant drawbacks, such as low conductivity and in‐plane packing that limits electrolyte diffusion. In this work, we explore the synthetic flexibility of α‐CoII hydroxides (Simonkolleite‐like structures) to overcome these limitations. We elucidate the growth mechanism of 3D flower‐like α‐CoII hydroxyhalides by using in situ SAXS experiments combined with thorough physicochemical, structural, and electrochemical characterization. Furthermore, we compared these findings with the most commonly employed Co‐based LHs: β‐Co(OH)₂ and CoAl layered double hydroxides. While α‐CoII LH phases inherently grow as 2D materials, the use of ethanol (EtOH) triggers the formation of 3D arrangements of these layers, which surpass their 2D analogues in capacitive behavior. Additionally, by taking advantage of their anion‐dependent bandgap, we demonstrate that substituting halides from chloride to iodide enhances capacitive behavior by more than 40 %. This finding confirms the role of halides in modulating the electronic properties of layered hydroxides, as supported by DFT+U calculations. Hence, this work provides fundamental insights into the 3D growth of α‐CoII LH and the critical influence of morphology and halide substitution on their electrochemical performance for energy storage applications.

Light-weight flexible symmetric supercapacitors based on magnesium-zinc codoped MnO2 nanostructures on carbon cloth as enhanced-performance binder-free electrodes

Developing advanced flexible supercapacitors with high energy and power density is a critical research goal. One promising approach involves combining manganese dioxide (MnO2) with a three-dimensional carbon substrate. This strategy leads to the creation of supercapacitor electrode materials that exhibit high specific capacitance, stability, and environmental friendliness. However, the challenge lies in addressing the low electrical conductivity of MnO2, which limits the rate of electron transfer. The incorporation of metal ions enhances the conductivity of manganese oxide, resulting in a significant increase in lattice defects. These defects create abundant active sites for energy storage. In this study, we developed flexible electrodes based on magnesium-doped MnO2, zinc-doped MnO2, and magnesium-zinc codoped MnO2 nanostructures deposited on carbon cloth (CC) via a one-step hydrothermal method. The supercapacitive behavior of these electrodes was investigated using CV and GCD measurements. The as-prepared electrodes exhibit good electrical conductivity, and their interconnected network structure, composed of sponge-shaped nanostructure layers, results in a large specific surface area. This network also facilitates efficient pathways for effective electron transport. The optimized Mg-Zn codoped MnO2@CC sample exhibits a high capacitance of 79.9 mF/cm² at 0.7 mA/cm² and good rate performance, reaching around 46.59 mF/cm² up to 1.5 mA/cm² in the three-electrode system. Notably, the areal capacitance values calculated from the CV curves for all Mg-Zn codoped MnO2@CC electrodes surpass those of Mg-doped MnO2@CC and Zn-doped MnO2@CC. A flexible symmetric supercapacitor assembled using the best Mg-Zn codoped MnO2@CC as both positive and negative electrodes and PVA-Na2SO4 gel electrolyte delivers a desirable energy density of 0.196 mWh/cm2 at 2.38 mW/cm2. Furthermore, this fabricated supercapacitor demonstrates a broad voltage window of 2.25 V and remarkable cycling stability, retaining 83 % of its initial performance after 4000 charge-discharge cycles.

Incorporating Ag into Nd-Succinate MOF: Tunned electrochemical supercapacitor behaviour of Ag modified Nd-Succinate and electrochemical reaction mechanism

The electrode materials must be tailored to achieve higher energy and power densities and thus improve the supercapacitor's performance. This study explores the impact of incorporating Silver (Ag) into a Neodymium-Succinate Metal Organic Framework (Nd-Succinate) on supercapacitor behaviour. Initially, the Nd-Succinate MOF was characterized by structural, morphological, and spectroscopic characterizations. Subsequently, Ag/Nd-Succinate was synthesized and characterized. The electrochemical performance of Ag/Nd-Succinate was evaluated in a 6 M KOH electrolyte; the results indicated a significant enhancement in supercapacitor performance upon incorporating Ag into parent Nd-Succinate. From galvanostatic Charge-Discharge cycles (GCD), the capacitance for Ag/Nd-Succinate was determined to be 1389 F/g, i.e., 42 % higher than that of bare Nd-Succinate which was measured at 978 F/g. at a current density of 1.25 A/g. Ag/Nd-Succinate showcased an 89 % retention value for multiple retention cycles, slightly higher than the retention value obtained (84 %) for Nd-Succinate. The results of electrochemical experiments (Cyclic voltammetry (CV) and Electrochemical Impedance Spectra (EIS)) provided information about the nature of electron transfer and capacitance enhancement upon the introduction of Ag into Nd-Succinate. These findings provide valuable information on modifying MOFs and introducing metal that will help produce high-performance supercapacitor electrodes.

Self-doped N, P, O heteroatoms carbon nano-hollow-fiber derived aromatic bio-organic for advanced gravi-volumetric supercapacitors

Abstract The combination of heteroatoms self-doping and nano-hierarchical-pore structure is essential in improving the physicochemical performance of gravi-volumetric scale supercapacitors based on biomass-derived carbon. Herein, this study used aromatic bio-organic waste from nutmeg leaves (Myristica fragrans Houtt) as raw materials due to their abundant dopant and high-potential unique nano-pore structure. A series of novel treatments were carried out using KOH immersion approach and bi-atmospheric (in N2 and CO2) pyrolysis to ensure the presence of rich heteroatoms and a defined pore structure. The results showed that KOH ratio in bi-atmospheric pyrolysis played an important role in the production of self-dopant N, O, and P. In addition, significant morphological changes were observed after the production process. The optimized material prepared at a ratio of 500 mmol g−1 showed rich heteroatoms dopant with values of 19.53%, 15.81%, and 3.01% for N, P, and O, respectively. The surface transformation of the products showed a unique structure of nano-hollow-fiber with a size of 8–12 nm size and a well-matched micro-mesopores ratio (4:1). In the 2E-symmetric system, the working electrode exhibited a high gravimetric capacitance of 235 F g−1 at 1 A g−1 and 210 F g−1 at 10 A g−1 (in H2SO4 electrolyte). The resulting energy output was relatively high at 32.64 Wh kg−1 with increased power density (218 W kg−1), coulombic efficiency (92.67%), and capacitance retention (89.78%). The findings also showed that the products obtained had a volumetric capacitance of 256.30 F cm−3 and volumetric energy of 35.00 Wh l−1. Based on these results, the selection of natural materials as well as the application of KOH immersion approach and bi-atmospheric pyrolysis produced natural self-doped N, O, P carbon nano-hollow-fiber for boosting the gravi-volumetric behavior of supercapacitors.

Modulation between capacitor and conductor for a redox-active 2D bis(terpyridine)cobalt(II) nanosheet via anion-exchange

Ionic polymers are intriguing materials whose functionality arises from the synergy between ionic polymer backbones and counterions. A key method for enhancing their functionality is the post-synthetic ion-exchange reaction, which is instrumental in improving the chemical and physical properties of polymer backbones and introducing of the functionalities of the counterions. Electronic interaction between host polymer backbone and guest ions plays pivotal roles in property modulation. The current study highlights the modulation of responses to external electric field in cationic bis(terpyridine)cobalt(II) polymer nanofilms through anion-exchange reactions. Initially, as-prepared chloride-containing polymers exhibited supercapacitor behaviour. Introducing anionic metalladithiolenes into the polymers altered the behaviour to either conductive or insulative, depending on the valence of the metalladithiolenes. This modulation was accomplished by fine tuning of charge-transfer interactions between the bis(terpyridine)cobalt(II) complex moieties and redox-active anions. Our findings open up new avenue for ionic polymers, showcasing their potential as versatile platform in materials science.

Architecture of interconnected cubic NiCo2S4 decorated mesoporous carbon with self-doped nitrogen based-hydrogel for high performance hybrid supercapacitor

Although the transition metal sulfides have shown persuasive proof and stellar traits for energy storage applications, their real applications still possess some obstacles such as prolonged ionic and electronic transport. Hence, NiCo2S4 decorated a pyrolyzed hydrogel (NiCo2S4@PHG) via facile synthesis is considered a promising electrocatalyst for energy storage devices. The prepared electrode materials were characterized utilizing different analysis techniques like XPS, XRD, FT-IR, TGA, SEM, TEM, elemental mapping and EDX that reveal the crucial role of the hydrogel pyrolysis in creating a homogenous nitrogen-doped carbon matrix. The as-fabricated 0.5 NiCo2S4@PHG nanocomposite was electrochemically examined in a sealed workstation cell and showed a clear battery-type supercapacitor behavior attributed to various redox reactions, porosity, and conductivity that was enhanced by self-doped nitrogen. In contrast, composites based on nickel and cobalt sulfides individually with pure hydrogel demonstrated the superiority of binary metal composites. The 0.5 NiCo2S4@PHG electrode exposed a marvelous specific capacity of 317.9 mAh g−1 and capacitance of 2728.5 F g−1 at a current density of 1 A g−1. A hybrid asymmetric supercapacitor was established by 0.5 NiCo2S4@PHG (cathode) and activated carbon (AC, anode), which brought large energy and power densities of 32.8 Wh kg−1 and 750 W kg−1, respectively. The fabricated cell manifests ultra-high retention of 82.6% at a current density of 20 A g−1 after 10,000 cycles. These outstanding accomplishments hold significant potential for practical energy storage and conversion applications.

Modeling the Dynamics of Supercapacitors by Means of Riemann–Liouville Integral Definition

The application of fractional calculus to obtain dynamic models for supercapacitors represents an alternative approach to obtaining simpler and more accurate models. This paper presents a model for the supercapacitor in the time domain, based on the use of the fractional or non-integer order integral. This fractional model is compared with the conventional simple model, which is typically used in industrial applications. This fractional integral-based model provides satisfactory fits in relation to the number of parameters used in the model. Furthermore, an interpretation of the effect of the application of fractional integration is presented for constant current charging and discharging processes at constant current, using the Riemann–Liouville definition for the non-integer order integral. Supercapacitors are devices that exhibit non-linear behavior, with a distinct charging and discharging operation. There are several methods of dynamic analysis for the characterization of supercapacitors. The information extracted from these methods is essential for understanding the behavior of supercapacitors and, thus, ensuring that processes involving supercapacitors are as efficient as possible. This paper presents a dynamic analysis based on charge and discharge operations with constant currents. The conclusion is that the fractional model provides fairly accurate fits.

(Nanocarbons Division Poster Award, 3rd Place) Hybrid Supercapacitance and Stability of Fe-Based Metal-Organic Frameworks/Graphene Oxide Nanoribbons Composite Allover the pH Range

Adopting renewable energy sources is growing fast, and hence it should be accompanied by tremendous efforts to develop energy storage technologies that can mitigate the intermittent nature of these sources. Supercapacitors (SCs) are considered among the most promising technologies for that purpose due to their high durability, power density, and charging/discharging competency. SCs have two types according to their electrochemical charge storage mechanism: pseudocapacitance (PCs) or battery-like behavior and electrochemical double-layer capacitors (EDLCs). The development of next-generation supercapacitors requires a holistic approach that integrates both mechanisms. Because of their huge surface area, porous structure, and abundance of active redox sites, metal-organic frameworks (MOFs) have exceptional potential in energy storage devices. However, due to the MOFs’ low conductivity and stability, they are in need to be mixed with highly conductive and stable materials such as carbon-based ones.In this work, Fe-based MOFs were selected to be responsible for mainly the battery-like contribution to the overall supercapacitance due to the presence of the redox-active sites. Even though little attention has been given to the Fe-based MOFs they showed a promising performance in several solutions, with low stability.1,2 To enhance the Fe-MOFs stability and conductivity and add an EDLC component to the overall capacitance behavior graphene oxide nanoribbon (GONRs) was used. The GONRs' exceptional properties such as ultrathin two-dimensional structures, superior mechanical behavior, strong chemical stability, and high electrical conductivity make them promising materials for supercapacitor applications.In this study, Fe-MOFs were synthesized using a hydrothermal method,3 and GONRs were prepared using an oxidative unzipping method.4 A composite of Fe-MOFs/GONRs was prepared by physical mixing. The physical and chemical properties of the synthesized Fe-MOFs, GONRs, and Fe-MOFs/GONRs were characterized using XRD, SEM, TEM, FT-IR, Raman spectroscopy, and XPS. Since the electrolyte properties have a substantial impact on the supercapacitive behavior and stability of the electrode materials, the specific capacitance of the prepared composites was measured in 1M H2SO4, 1M KOH, 1M K2SO4, and 1M KCl utilizing different evaluation systems (three and two-electrode systems). The Fe-MOFs/GONRs composite showed a significant synergistic effect in comparison to its pure components. Further discussion will be given regarding the pH and ion size/type effect on the supercapacitive performance and stability.

Effect of Functionalized Carbon Nanotubes and Graphene Oxide Nanoribbons on the Supercapacitive Behavior of Zr-Based Metal-Organic Frameworks in Acid Media

Metal-organic frameworks (MOFs) as a kind of crystalline porous materials have attracted much attention due to their high surface area and high electrochemical performance as electrode materials in supercapacitors 1. Recently, there has been a lot of interest in functionalized multiwalled carbon nanotubes (F-MWCNTs) based materials and especially graphene oxide nanoribbons (GONRs), which have unusual characteristics of ultrathin two-dimensional structures and, as promising materials for supercapacitors and other electrochemical energy storage devices. The F-MWCNTs and GONRs' high electrical conductivity, highly changeable surface area, strong chemical stability, excellent mechanical behavior, and capacity to modify attributes for the desired application are behind the reasons for choosing to make a composite of these materials with Zr-MOF 2.In this work, Zr-MOF was synthesized using the solvothermal method 3, MWCNTs were functionalized using acid washing (3 M H2SO4: 1 M HNO3), and GONRs were fabricated using the oxidative unzipping method 4. The Zr-MOF/F-MWCNTs and Zr-MOF/GONRs composites were prepared through physical mixing. The physical and chemical structures of the synthesized Zr-MOF, F-MWCNTs, and GONRs were evaluated using XRD, SEM, TEM, FT-IR, Raman spectroscopy, and XPS. The supercapactive behavior of the prepared composites was evaluated in comparison to their components (Zr-MOF, F-MWCNTs, and GONRs) in 1M H2SO4 utilizing various evaluation systems (three and two-electrode systems). Zr-MOFs showed a high specific capacitance (248 F/g at 1 A/g), making it a promising supercapacitor electrode material. That performance is dramatically improved by the addition of the nanocarbon materials (F-MWCNTs and GONRs). Zr-MOF-GONRs showed the highest specific capacitance (448 F/g at 1 A/g), with a large potential window (1.7 V) in the three-electrode system extended to (2V) in the two-electrode system, and good stability over 10,000 cycles at a high current density of 10 A/g. Reference: (1) Tan, Y.; Zhang, W.; Gao, Y.; Wu, J.; Tang, B. Facile Synthesis and Supercapacitive Properties of Zr-Metal Organic Frameworks (UiO-66). RSC Adv. 2015, 5 (23), 17601–17605. https://doi.org/10.1039/c4ra11896k.(2) Shrivastav, V.; Sundriyal, S.; Tiwari, U. K.; Kim, K. H.; Deep, A. Metal-Organic Framework Derived Zirconium Oxide/Carbon Composite as an Improved Supercapacitor Electrode. Energy 2021, 235, 121351. https://doi.org/10.1016/j.energy.2021.121351.(3) Abdelhamid, H. N. UiO-66 as a Catalyst for Hydrogen Production: Via the Hydrolysis of Sodium Borohydride. Dalton Trans. 2020, 49 (31), 10851–10857. https://doi.org/10.1039/d0dt01688h.(4) Kosynkin, D. V.; Higginbotham, A. L.; Sinitskii, A.; Lomeda, J. R.; Dimiev, A.; Price, B. K.; Tour, J. M. Longitudinal Unzipping of Carbon Nanotubes to Form Graphene Nanoribbons. Nature 2009, 458 (7240), 872–876. https://doi.org/10.1038/nature07872.

Preparation and Supercapacitive Behaviors of the Porous Reduced Graphene Derived from the Graphite Anode of Spent Lithium-Ion Batteries

Preparation and Supercapacitive Behaviors of the Porous Reduced Graphene Derived from the Graphite Anode of Spent Lithium-Ion Batteries

Magnetic transition magnetocaloric and supercapacitor behavior in synthesized Sn0.6Mn0.1Ge0.3Te alloys

This study comprehensively investigates the structural, microstructural, vibrational, magnetic, and magnetocaloric properties of novelty Sn0.6Mn0.1Ge0.3Te alloys synthesized using the sealed tube solid-state reaction method. The observed magnetic behavior showcases a transition from paramagnetic (PM) to ferromagnetic (FM) phases at the Curie temperature TC = 29 K. Notably, magnetic entropy change (−ΔSM), relative cooling power (RCP), and refrigerant capacity (RC) are calculated as 1.5 J/kg-K, 42.05 J/kg, and 37.39 J/kg, respectively, under a magnetic field of 60 kOe. Arrott curve analysis further validates the magnetic phase transition, affirming a second-order transition between FM and PM phases. Critical exponents (β, γ, and δ) are derived from field-dependent magnetic entropy changes around the second-order transition and strongly agree with the mean field model. These critical exponents establish a clear correlation between critical behavior and magnetocaloric effects, reinforcing the potential of Sn0.6Mn0.1Ge0.3Te alloys for magnetocaloric applications. Investigations into the electrochemical properties of the alloy have indicated that it exhibits a specific capacitance of 152.9 F/g at a scan rate of 20 mV/s, demonstrating a predominantly pseudocapacitive charge storage mechanism. Additionally, the alloy has proven to be highly stable, retaining 94.2 % of its specific capacitance after 10,000 cycles.