Specific Capacitance Value Research Articles

Electrochemical and photoluminescence properties of Ce3+ doped copper aluminate nanoparticles

In this communication, for the first of its kind, CuAl2O4 doped with Ce3+ (1-9 mol %) are syn- thesized by solution combustion method using Aloe Vera gel as a reducing agent. The as-formed sample was calcined at 500° C for 3 hours, followed by characterization. The addition of dopants to the copper aluminate matrix didn't alter the crystal structure of the host matrix. Bragg reflec- tions confirm the formation of the cubic phase and also absence of other impurities. The surface morphology consists of nanorods arranged one above the other. The estimated crystallite size was found to decrease from 12 to 9 nm whereas, the direct energy band gap increases from 2.84 to 3.02 eV with an increase in dopant concentration. Under λex = 305 nm excitation, photoluminescence (PL) emission spectra have a high intense peak at 553 nm along with a less intense peak at 472 nm. The peak at 553 nm can be attributed to the existence of oxygen vacancies which arise due to the transition of an electron from the 2D3/2→2F7/2 of Ce3+, however, the peak observed at 472 nm results from the transition of ionized oxygen vacancies (VO) to the valence band caused by the 2D3/2→2F5/2 transition. The CIE coordinates lie well within the green region with 5758 K aver- age CCT. Further, Cyclic voltammetry analysis was conducted to investigate oxidation and redox peaks, while electrochemical impedance spectroscopy provided insights into ion transport kinetics. Specific capacitance values ranging from 29 to 59 F/g were obtained for CuAl2O4:Ce(1-9 mol %) NPs. These findings suggest potential applications for the synthesized material in areas such as display technology as a green nano phosphor and energy storage materials.

Bulk scale synthesis of high-performance carbon nanomaterial from biogas plant residual waste: Tuned porosity and composition for advanced supercapacitor applications

Carbon based nanomaterials with tuned porosity and compositions are of great interest in terms of energy storing materials. Nevertheless, it is still a challenge to produce such nanostructures on a large scale in cost-effective manner. In this work, we demonstrate that carbon nanomaterial (CNM) can be prepared using biogas plant residual waste (BPRW) as the precursor on a bulk scale under the specific two step pyrolysis technique. The optimized process along with the catalyst used is crucial as the simple pyrolysis of precursor can only produce traditional activated carbon with significantly lower specific capacitance values. The spherical structure of silica nanoclusters and graphitic skeleton of synthesized CNM confirmed with the help of FE-SEM, AFM and HR-TEM along with Raman and XRD while EDX, XPS, and FT-IR studies confirm the presence of various functional groups along with their respective percentage composition. These CNMs show mesoporous structure of the nanomaterial. Among three different aqueous electrolytes, the maximum specific capacitance of 371.88 Fg−1 at 0.5 Ag−1 current density in 1 M H2SO4 indicates its suitability for the practical supercapacitor applications. The fabricated symmetric supercapacitor device using CNMs as the electrode material and 1 M H2SO4 as the electrolyte shows very good specific capacitance value with the high energy density of 34.4 Whkg−1 corresponding to 360 Wkg−1 power density along with the good cyclic stability over 10,000 cycles of charge–discharge. This innovative technique paves the way towards upcycling any lignin containing waste material into carbon-based nanomaterial on a bulk scale by an effective method, which can be further used as high-performance electrode material for energy storage applications like in supercapacitors and batteries.

Sustainable production of in-situ activated carbon from arecanut husk and their supercapacitor applications

A facile and sustainable method is adopted for the synthesis of activated carbon from arecanut husk biomass. The inherent potassium enrichment in arecanut husk is exploited for an in-situ activation process. The activated samples exhibited an optimal porosity with abundant meso/micro pores and channels making them a promising candidate for supercapacitor applications with a specific capacitance value as high as 217 Fg−1 as calculated from the CV curves. The values for non activated and KOH activated carbon samples derived from arecanut husk were only 60 and 80 % of this value respectively. A fully functional symmetric supercapacitor prototype was also fabricated which exhibited a capacitance value of 46.2 Fg−1 with an energy density of 6.1 Whkg−1 at a power density of 270 Wkg−1.

Tuning capacitance of bimetallic ZnCo2O4 using anionic, cationic and non-ionic surfactants by hydrothermal synthesis for high-performance asymmetric supercapacitor

Surface properties of nanomaterials are directly related to their electrochemical performance, with surfactants playing an essential role in their cost-effective synthesis as structure-directing agents and templates. This research article discusses the effects of neutral, cationic, and anionic surfactants on the capacitance of bimetallic ZnCo2O4 nanomaterial, synthesized via a straightforward hydrothermal-annealing method. We investigated how cationic (cetyl-trimethyl ammonium bromide), anionic (sodium dodecyl sulphate), and non-ionic (urea) surfactants influence the electrochemical characteristics of ZnCo2O4 nano-powders. All three surfactant-based ZnCo2O4 electrodes exhibited Faradaic behaviour during electrochemical tests. The ionic nature of the surfactants significantly impacted the charge-storage mechanism, with specific capacitance values rising in the order of Urea (550 Fg−1) < C-TAB (740 Fg−1) < SDS (980 Fg−1) at a 1 Ag−1 in half-cell studies. The ZnCo2O4-SDS displayed the highest surface redox reactivity and superior electrochemical performance, with 426 Fg−1 in full-cell studies, energy density of 230 WhKg−1 (1 Ag−1), power density of 18,213.9 WKg−1 (10 Ag−1), and 93 % capacitance retention is observed over 50,000 cycles (50 Ag−1).

Ultrasonic assisted synthesis of nanoporous carbon/CeVO4 nanocomposite for supercapacitor and photocatalytic applications

Here, nanoporous carbon (NPC)/CeVO4 nanocomposite synthesized via ultrasonic assisted method for supercapacitor and tartrazine dye degradation application. Transmission electron microscope (TEM) studies confirmed the CeVO4 nanoparticles well embedded on the NPC surface in the NPC/CeVO4 nanocomposite. Spherical shaped CeVO4 nanoparticles are well incorporated on the surface of NPC therefore NPC/CeVO4 nanocomposite which possess a porous-like structure would improve the supercapacitor applications and dye degradation performance. As expected, the specific capacitance (Cs) values (555 F g−1) of NPC/CeVO4 nanocomposite showed enhanced performance as compared to CeVO4 nanoparticles (234 F g−1) at a current density of 1 A g−1 and the capacitance retention of the designed electrode as 95 % after 5000 cycles. The photodegradation of tartrazine dye using pure CeVO4 nanoparticles and NPC/CeVO4 nanocomposite was explored under visible light irradiation. The photocatalytic degradation experiment demonstrated that the NPC/CeVO4 exhibits the maximum degradation efficiency (98.76 %) of the tartrazine with was reached within 120 min. Moreover, the rate constant of NPC/CeVO4 for tartrazine dyes decomposition was 0.0192 min−1 representing that it is two-fold higher than pure CeVO4 (0.0073 min−1). The superior electrochemical and photocatalytic properties of NPC/CeVO4 nanocomposite have been observed due to the well-designed structure and high surface area. Consequently, as-prepared NPC/CeVO4 material could be a promising material for electrochemical supercapacitor and dye degradation of the tartrazine organic pollutant.

Comparative study of the electrochemical characteristics of activated carbons from biomass waste as symmetrical supercapacitor

Surface, structural and electrochemical analysis of a series of activated carbons obtained from biomass waste was carried out. It has been shown that the proportion of surface oxygen has a significant dependence on the type of feedstock. Minimum oxygen values are shown for activated carbons from precursors obtained as a result of deep processing of cellulose. Structural analysis carried out by two methods showed that the main differences between activated carbons are concentrated in the mesopore region, while the volumes of micropores for all samples are close to each other. For two samples with maximum surface areas, studies of the hydrophobic properties of the surface were carried out. Comparison of structural data with electrochemical impedance results showed a high correlation between mesopore surface area data and the effective conductivity of electrodes in the cells of a symmetrical supercapacitor. A comparison was made of the specific capacitance values obtained by cyclic voltammetry, impedance measurement and galvanostatic discharge. A study of the effect of charging time on the energy characteristics of cells showed an abnormally high power of an electrode made on the basis of lignin. The types of materials applicable to electrodes in electric energy storage devices have been determined.

Unveiling the mass-loading effect on the electrochemical performance of Mn3O4 thin film electrodes: A combined computational and experimental study

Abstract The remarkable storage performance of manganese oxide (Mn3O4) makes it an appealing option for use as electrodes in electrochemical capacitors. However, the storage kinetics were significantly influenced by the mass loading of the electrode. Herein, we have inspected the dependency of mass loading on the storage performance of the spray pyrolyzed Mn3O4 thin film electrodes along with the correlation of structural and morphological characteristics. X-ray diffraction and Raman spectroscopic studies proven the formation of spinel Mn3O4 with a tetragonal structure. Morphological analysis revealed that all films exhibited fibrous structures with interconnected patterns at higher mass loadings. Moreover, the surface roughness and wettability of the electrode surface were influenced by variations in mass loading. Notably, thin-film electrode with a mass loading of 0.4 mg/cm2 exhibited the highest specific capacitance value of 168 F/g at 5 mV/s in a three-electrode system. Further, electrochemical impedance spectroscopic studies showed that there were noticeable changes in the capacitive behaviour of the electrode with respect to variations in mass loading. Moreover, the Dunn approach was employed to differentiate the underlying storage mechanism of the Mn3O4 electrode. Additionally, first-principles Density Functional Theory (DFT) studies were carried out in connection with the experimental study to comprehend the structure and electronic band structure of Mn3O4. This study underscores the critical importance of mass loading for enhancing the storage performance of Mn3O4 thin-film electrodes.&amp;#xD;

Electrochemical properties of binder-free micro-blocks/sheets-based cadmium‑nickel-sulfide electrode materials for portable energy storage applications

The major goal of community is to synthesis the novel electrode materials for new energy storage sources to reduce the environmental pollution and to overcome the energy crises in developing countries. Herein, the authors synthesized a binder-free micro-blocks/sheets-based nickel sulfide, cadmium-sulfide‑nickel-sulfide (Ni-S, Cd-S-Ni-S) electrode materials (EMs) on nickel foam by home-made chemical vapor deposition technique. The XRD patterns reveals the development of polycrystalline Ni-S, Cd-S-Ni-S phases. The average crystallite size of Ni-S and Cd-Ni-S EMs are found to be ⁓32 to ⁓45 nm respectively. The microstructure of Ni-S is changed from cluster-of-nanoparticles/micro-blocks to nanosheets when a layer of Cd-S is condensed on Ni-S EMs. The EDX analysis confirms the presence of various wt% of Ni, Cd and S in Ni-S, Cd-S-Ni-S EMs. The molar ratios of Ni and S are found to be 1.46 and 0.46 in the synthesized Ni-S EMs. The molar ratios of Ni, Cd and S are found to be 0.459, 0.439 and 0.702 in the synthesized Cd-S-Ni-S EMs. The maximum values of specific capacitance, energy density and power density of Ni-S and Cd-S-Ni-S EMs are found to be 3305, 4086 F/g at 1 mV/s 25 Wh/kg and 1399 W/kg respectively. The capacitive contribution of Cd-S-Ni-S EMs is higher than Ni-S EMs, however, it is increased with increasing scan rates. The excellent capacity retention (75–92 %), good cyclic stability, impedance analysis show that the synthesized Ni-S, Cd-S-Ni-S EMs are suitable for energy storage devices like supercapacitor and batteries.

A thiophene-sulfur doping porous organic Polymer/reduced graphene oxide composite for high-performance supercapacitor electrode

Porous organic polymers (POPs) are a type of promising materials which can be used in energy storage devices. In this study, we synthesized a novel thiophene-sulfur doping POPTAB-TPDA through Schiff-base condensation reaction between 1,3,5-triaminobenzene (TAB) and 2,5-thiphenedialdehyde (TPDA) at ambient temperature and pressure. With the reduced graphene oxide (rGO) as a template, thiophene-sulfur doping POPTAB-TPDA-rGO composite was obtained by in-situ synthesis under the same condition. As supercapacitor active electrode material, the stable value of specific capacitance of the POPTAB-TPDA-rGO composite (232.4 F g−1) is higher than that of pristine POPTAB-TPDA (193.5 F g−1) at a current density of 0.5 A g−1. The assembled asymmetric supercapacitor utilizing POPTAB-TPDA-rGO composite as positive material has an energy density of 38.7 W h kg−1 with the power density of 1619.2 W kg−1, displaying a better result than POPTAB-TPDA-based device. Furthermore, the POPTAB-TPDA-rGO-based supercapacitor exhibits an excellent cycle duration, with 81.7 % retention of its highest capacitance after 7000 cycles. This superior electrochemical performance of the composite could be attributed to three aspects: the reversible redox reaction processes of thiophene-sulfur units, the porous structure of POPTAB-TPDA facilitating ion transmission, and the good electron conductivity of rGO template.

An insight into the electrochemical performance of nanostructured V2O5 in aqueous neutral electrolytes and fabrication of 2V, high energy density, symmetric supercapacitor

The exceptional redox characteristics, simple methods of synthesis, low cost and wide range of oxidation states of transition metal oxides like V2O5 have made them highly sought after electrode materials for supercapacitors. In the present study, V2O5 nanostructures prepared via a facile microwave-assisted method is used as the electrode material. The electrochemical performances of this electrode material is analysed in four different aqueous neutral electrolytes. The nature of the ions present in the electrolytes are found to have a significant influence on the performance of the electrode, achieving the highest specific capacitance values in KCl electrolyte while highest potential window and stability in Na2SO4 electrolyte. The symmetric supercapacitor fabricated using the Na2SO4 electrolyte exhibits a specific capacitance value of 82.35 F g-1 and a specific energy of 45.75 Wh kg-1 at a specific power of 1000 W kg-1. Moreover, the device retains 70 % of its initial capacitance even after 10,000 charge-discharge cycles at a current density of 5 A g-1. An asymmetric supercapacitor is also fabricated using KCl electrolyte after optimizing the mass-ratio of positive and negative electrodes using Ragone plot simulator. The asymmetric supercapacitor exhibits a specific capacitance of 34 F g-1 with an energy density and power density of 11 Wh kg-1 and 775 W kg-1 respectively. The present study summarizes the effect of different neutral electrolytes on the electrochemical performance of V2O5 nanostructured electrodes. The physiochemical properties of ions such as solvation, diffusion and mobility, and their influence on the electrochemical behaviour are also taken in to account to explain the observed electrode performance.

High-performance pseudo-capacitance supercapacitor with highly mesoporous fluorine doped polymeric carbon nitride nanosheets as electrode material

In this study, graphitic carbon nitride (GCN) material obtained from urea was hydrothermally doped with fluorine atoms (F-doped GCN). The resulting F-doped GCN material was designed as an electrode material for supercapacitors. Characterization of these samples was carried out by XRD, EDS, SEM, nitrogen adsorption and FTIR analyses. EDS and FTIR analyses confirmed the doping of fluorine atoms onto GCN. Nitrogen adsorption analyses supported the formation of a significant mesoporous structure with fluoride doping on GCN. The specific capacitance values of the GCN and F-doped GCN supercapacitors were calculated as 39.75 F/g and 305.72 F/g at a frequency of 0.01 Hz. A significant increase of about 7-fold in capacitance value was obtained by fluorine doping on GCN. Cycling trials of the F-doped GCN supercapacitor for up to 1000 cycles at a current density of 0.4 A/g maintain an efficiency of 86.72 %. For the supercapacitor designed from F-doped GCN material, the maximum energy density and power density were calculated as 4.26 Wh/kg and 1792 Wh/kg, respectively.

Mg‐ZnO/CNT Nanocomposite as Electrode Materials with Enhanced Electrochemical Performance for Supercapacitor Applications

AbstractThe present research work reported the study of nanocomposites of undoped and Mg‐doped ZnO with CNT as electrode materials for supercapacitor application. The undoped ZnO/CNT and Mg‐doped ZnO/CNT nanocomposites (i.e., 10 % Mg‐doped and 20 % Mg‐doped) were synthesized using a cost‐effective blending‐assisted hydrothermal method. The morphological (FESEM &amp; TEM) studies revealed that the diameter of CNT was ~7 nm and the ZnO nanoparticles were spherical in shape with an average particle size of ~5 nm. In addition, it was also found that 10 % Mg‐ZnO and 20 % Mg‐ZnO had a sheet‐like structure. XRD and FTIR studies further confirmed the successful doping of Mg in ZnO and CNT nanocomposites. BET analysis showed that the value of specific capacitance increased with the increase in surface area. Further, the electrochemical performance of these nanocomposites revealed that the higher doping percentage, 20 % Mg‐ZnO/CNT nanocomposite achieved the highest specific capacitance value i.e., 458.5 F/g at 0.1 A/g current density in 3M H2SO4 electrolytic solution, having a retention of 99.8 % after 12,00 long cycles. In addition, the charge storage mechanism revealed that the as‐synthesized nanocomposites showed both the diffusion‐controlled and capacitive‐controlled behaviors. Thus, a higher value of specific capacitance with excellent cyclic stability indicated the higher efficiency of Mg‐doped ZnO/CNT nanocomposite for future supercapacitor applications.

Zeolitic imidazolate framework derived stellate shaped cobalt-molybdenum hybrid sulfide microflower for enhanced supercapacitor properties

Zeolitic imidazolate frameworks (ZIFs) represent a class of material exhibiting a well-defined geometry. The ZIF derivatives are known to inherit the parent morphology and have emerged as a potential platform for developing superior electrode materials. In this study, leaf-like ZIF-67 is synthesized using a chemical route and employed as the sacrificial template in one-pot hydrothermal sulfurization for preparing Co3S4-Mo15S19, cobalt‑molybdenum hybrid sulfide (CMS/NF). The unique stellate-shaped architecture of the CMS/NF microflowers enhances the exposure of the redox active sites, improving charge storage and exhibiting superior performance. On account of the synergy of the metal ions and stellate-shaped hierarchical architecture, the CMS/NF hybrid sulfide shows an excellent specific capacitance value of 3283 F g−1 at a current density of 1 A g−1 with capacitance retention of 77.7 % at 10 A g−1. An asymmetric supercapacitor device based on CMS/NF hybrid sulfide with aqueous KOH electrolyte exhibits a high specific energy of 40.8 Wh kg−1 at 400 W kg−1 with excellent cycling life of 81 % after 5000 cycles with ∼100 % coulombic efficiency. In addition, the density functional theory-based simulations have been carried out for the Co3S4-Mo15S19 hybrid system to develop a better understanding. From the total density of states, it is concluded that compared to the pristine structures, the hybrid system has enhanced states close to the Fermi level, confirming the conductivity improvement. Computed quantum capacitance for the pristine and hybrid systems corroborates the experimental capacitance consequences. Hence, the theoretical examinations warrant our electrochemical results and provide insight into developing high-performance supercapacitor electrodes.

New Hybrid Materials Based on N-Doping Copolymers of Thiophene Derivatives for Electrochemical Energy Storage

Over the past decade, electroactive conducting polymers (ECPs) are among the most potential pseudocapacitive materials for the electrodes of microsupercapacitors. ECPs exhibit several advantages, such as good conductivity (up to 103 S cm-1), flexibility, high specific capacitance (values ranging from 300 to 800 F.g-1 depending on synthesis and electrochemical performance conditions), relatively cheap and ease of synthesis [4]. Therefore, the electrochemical deposition of ECPs revealed a new strategy to design a great variety of various polymer morphologies as an innovative pseudocapacitive materials. Based on the different storage mechanism, electrochemical supercapacitors can be divided into three types, namely electrochemical double layer capacitors (EDLCs), pseudosupercapacitors and hybrid supercapacitors in which ECPs and other pseudocapacitive materials such as carbon materials, transition metal oxides, nitride complexes allow to store higher amount of capacitance per gram (faradic reactions) than EDLCs (pure capacitive energy storage reaction).In this work, we have elaborated new n-doped conducting polymers Poly[3,6-bis(2-thienyl)pyridazine] and Poly[3,6-bis(2-(3-n-hexylthienyl))pyridazine] by making electropolymerization on Pt disk electrode and 3 nm alumina coated silicon nanowires in acetonitrile organic electrolyte. The comonomers 3,6-bis(thienyl)pyridazine and (3,6-bis(2-(3-nhexylthienyl))pyridazine) have been successively synthesized. The produced polymeric materials Poly[3,6-bis(2-thienyl)pyridazine] and Poly[3,6-bis(2-(3-n-hexylthienyl))pyridazine] during n-doping process on Pt working electrode in acetonitrile solution of TBAPF6 (0.1 M) expose very low potential value of -2.23 V and -2.19 V at current density of -0.25 mA.cm-2 and -0.06 mA.cm-2, respectively. The elctropolymerization of synthesized comonomer 3,6-bis(thienyl)pyridazine has been done on Al2O3@SiNWs and resulted in thin layer of polymer film with micropores. The experimental results are compared to electropolymerization study of thiophene monomer on Pt disk and Al2O3@SiNWs electrodes to highlight the similarities and electrochemical advancements.

Improved Structural and Electrochemical Properties of Mg-Doped Nickel Cobaltite Nanoparticles Synthesized Using Low-Temperature Microwave Hydrothermal Method

The specific capacitance of materials influences the energy storage capacity. A series of MgxNi1-xCo2O4 (x = 0.0 - 0.1) nanoparticles using the low-temperature microwave-hydrothermal (M-H) method at 160 0C temperature, and sintered at 600 °C. The samples were then characterized using X-ray diffraction (XRD), Field Emission Scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). It is observed from X-ray diffraction that all the samples are cubic spinel in nature with space group Fd-3m, and the lattice parameter varies between 8.097 (x = 0.0) and 8.083 (x = 0.10). The nanoparticles have a hexagonal nanoflake-like shape morphology with an average particle size of 180 nm to 350 nm. The tetrahedral and octahedral absorption bands were observed at 561 cm-1 and 654 cm-1, respectively. The valence states of Ni2+/Ni3+, Co2+/Co3+, and Mg2+ were confirmed by X-ray photoelectron spectroscopy. The electrochemical studies using CV and GCD were performed on all the samples. High values of specific capacitance of 332 F g−1, energy densityof 9.05 Wh kg-1, and power density of 224.84 W kg-1 were observed for the sample x = 0.08. Therefore, Mg0.08Ni0.92Co2O4 sintered at 600 °C shows good impedance and electrochemical properties, which are helpful for supercapacitor applications. Figure 1

Incorporation of nitrogen and oxygen in carbon: A highly tuned electrochemistry with facile synthesis and its influence on optical and electrode performance in supercapacitors

A new approach for synthesizing heteroatom-doped carbon nanostructures has been developed, in which nitrogen and oxygen have been effectively infused into the graphitic core using the required precursors. The heteroatoms incorporated into the carbon matrix and their corresponding structural features are examined. The observed X-ray diffraction pattern reveals the presence of amorphous carbon forms that resemble carbon nitride in their structure. The presence of additional N–O and C–O bonds gives strong evidence of a graphitic structure with oxygen and nitrogen incorporation, as shown by the Fourier transform-infrared peaks. The X-ray photoelectron spectroscopy analysis reveals important information regarding the bond formation in the graphitic core of the sample. The study focused on examining the porous and intricately interconnected network structures, showcasing a variety of particle morphologies, and was carried out using scanning electron and transmission electron microscopy. The lattice defects are investigated using transmission electron microscopy-high angle annular dark field technique to explore the surface morphology. The influence of incorporated O and N in carbon structure drastically reduced the electron density of the graphitic core. As a result, the absorption bands observed were around 300–400 nm, showing the semiconductors' absorption characteristics. Three-electrode electrochemical systems are fabricated with working electrodes based on COx and CNx materials. The COx and CNx-modified electrodes were meticulously tested for their performance in supercapacitor applications. The COx samples exhibit a significant specific capacity value of 439.20 C g−1 under a low current density of 4 A g−1. The CNx samples demonstrate a specific capacity of 420.00 C g−1 under 4 A g−1 current density.

Optimizing Energy Storage Performance: In situ Synthesized Manganese Oxide (Mn3O4) Nanoparticle‐Based Symmetric Supercapacitor on a Paper Substrate

AbstractIn this study, a redox reaction is employed to synthesize manganese oxide (Mn3O4) nanoparticles using potassium permanganate as a precursor in the presence of diethyl amine. The structural characterization reveals the formation of the tetragonal phase of Mn3O4 nanoparticles with a space group of I41/amd. A free‐standing Mn3O4‐based paper electrode is fabricated and its electrochemical performances are investigated. The electrode exhibits a maximum specific capacitance value of ~353 F g−1 and an areal capacitance of ~530 mF cm−2 at a current density of 0.2 A g−1. A symmetric supercapacitor‐based device is also designed using Mn3O4 nanoparticles as an active material in a gel electrolyte configuration. The Mn3O4 device achieves specific and areal capacity values of ~208 mAh g−1 and 260 mA cm−2, respectively, at a current density of 0.3 A g−1. The device delivers maximum energy and power density values of ~104 Wh kg−1 and ~220 W kg−1, respectively, with ~92 % specific capacity retention at 0.3 A g−1 after 5000 cycles. The above results suggest that the Mn3O4‐based device has the potential for energy storage applications.

Pseudocapacitive Electrode Based on MnO2 Loaded Activated Charcoal on Graphite Paper for Sustainable Energy Storage

AbstractThe design of high‐performance electrode material without compromising energy and power density is critical for the advancement in hybrid electric vehicle technology. In this perspective, we have fabricated a MnO2 loaded activated charcoal‐based electrode on graphite paper as an endeavour to improve the energy storage capabilities. The electrode material is synthesized by employing a sustainable route and the structural, microstructural, and textural properties have been investigated. The electrochemical performance for energy storage is evaluated and the fabricated electrode on graphite paper exhibits remarkably high‐power density (811 W kg−1) maintaining high energy density (106 Wh kg−1) at the same time, along with high gravimetric specific capacitance value of 768 F g−1 at 2 mA cm−2. The obtained results demonstrate the excellent performance of the electrode material, suggesting MnO2 loaded activated charcoal as a prospective electrode material to meet the demand of hybrid electric vehicles as well as to contribute to our transitioning towards low‐to‐zero carbon emission technology.

Supercapacitor properties of partially oxidised-MXene quantum dots/graphene hybrids: Fabrication of flexible/wearable micro-supercapacitor devices

Recently, combining the synergistic properties of two-dimensional (2D) and zero-dimensional (0D) materials has attracted significant attention for energy applications. Here, we report the synthesis and characterization of partially oxidised-MXene quantum dots (PO-MXQDs) and reduced graphene oxide composite (PO-MXQDs/rGO) and investigate the resulting composites for energy storage applications towards supercapacitors. Density functional theory (DFT) simulations are used to examine the electrical and structural features of PO-MXQDs/rGO by predicting the chemical interaction involving charge transfer from PO-MXQDs to rGO. The multilayer Artificial Neural Network (ANN) model with hyperparameter tuning was developed at different input parameters to optimize material compositions, concentrations, and types of electrolytes to obtain the suitable conditions for best supercapacitive performance. The optimized PO-MXQDs/rGO showed a specific capacitance value of 1137.8 F.g−1 and was utilized for the fabrication of flexible micro-supercapacitors (FMSCs) device through the mask-assisted vacuum filtration process and asymmetric coin-cell type supercapacitor devices (ACCDs). The FMSCs deliver a higher areal capacitance (5.26 mF.cm−2), high areal energy density (0.46 μWh.cm−2), high areal power density (210.48 μW.cm−2), and the FMSC device has ultra-high cyclic stability up to 30000 cyclic voltammetry (CV) cycles. This method provides an in-depth study on developing 0D-2D hybrid materials with the wisdom of machine learning (ML) and DFT toward energy storage applications.

An efficient and green strategy for the synthesis of graphene with aqueous polyphenol extracts of orchid flower (Dendrobium Anosmum) for charge storage

This study introduces the use of orchid flower extract as a green reducing agent for the first time to produce reduced graphene oxide (ORGO). Raman, XRD and FTIR confirmed the reduction process whereas TGA analysis provides the thermal stability of the prepared samples. SEM imaging validates the improved morphology of ORGO as compared to the crumpled and folded region of graphene oxide (GO). Electrochemical tests reveal ORGO’s superior specific capacitance (489.8F/g) value at scan rate of 20 mV/s, low charge transfer resistance (2.1 Ω) and high specific capacity retention (96.63 %) after 10,000 cycles, highlighting its potential application for charge storage devices.