Search Results (55)

To develop high-performance electrode materials for supercapacitors, in this paper, a heterostructured composite material of cerium sulfide and zinc sulfide quantum dots (CeS₂/ZnS QD) was successfully prepared by hydrothermal method. Characterization through scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) showed that ZnS QD nanoparticles were uniformly composited with CeS₂, effectively increasing the active sites surface area and shortening the ion diffusion path. Electrochemical tests show that the specific capacitance of this composite material reaches 2054 F/g at a current density of 1 A/g (specific capacity of about 256 mAh/g), significantly outperforming the specific capacitance of pure CeS₂ 787 F/g at 1 A/g (specific capacity 98 mAh/g). The asymmetric supercapacitor (ASC) assembled with CeS₂/ZnS QD and activated carbon (AC) retained 84% capacitance after 10,000 charge–discharge cycles. Benefited from the synergistic effect between CeS₂ and ZnS QDs, the significantly improved electrochemical performance of the composite material suggests a promising strategy for designing rare-earth and QD-based advanced energy storage materials. Full article

This study employed a simple and cost-effective method for developing NiO with reduced optical band gaps that can be combined with nanostructured polyaniline (PANI). The composite systems were used as electrocatalytic and electrode materials in oxygen evolution reactions (OER) and in supercapacitor applications. We prepared the composite material in two stages: NiO was prepared with a reduced optical band gap by combining it with wheat peel extract. This was followed by the incorporation of PANI nanoparticles during the chemical oxidation polymerization process. A variety of structural characterization techniques were employed, including scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). A surface-modified NiO/PANI composite with enhanced surface area, fast charge transfer rate, and redox properties was produced. When NiO/PANI composites were tested in KOH electrolytic solution, 0.5 mL of wheat peel extract-mediated NiO/PANI demonstrated excellent electrochemical performance. It was found that the asymmetric supercapacitor (ASC) device had the highest specific capacitance of 404 Fg⁻¹ at a current density of 4 Ag⁻¹. In terms of energy density and power density, the ASC device was found to have 140 Whkg⁻¹ and 3160 Wkg⁻¹, respectively. The ASC device demonstrated excellent cycling stability and charge storage rates, with 97.9% capacitance retention and 86.9% columbic efficiency. For the OER process, an overpotential of 320 mV was observed at a current density of 10 mA/cm². It was found that the NiO/PANI composite was highly durable for a period of 30 h. A proposed hypothesis suggested that reducing the optical band gap of NiO and making its composites with PANI could be an appealing approach to developing next-generation electrode materials for supercapacitors, batteries, and fuel cells. Full article

This study aims to develop high-performance nickel selenide (NiSe) electrodes via a controlled electrodeposition approach, optimizing the number of deposition cycles to enhance electrochemical energy storage capabilities. Nickel selenide electrodes were synthesized at varying electrodeposition cycles (2CY–5CY) and systematically evaluated in both three-electrode and asymmetric supercapacitor (ASC) configurations to determine the optimal cycle for superior performance. Among all, the NiSe-3CY electrode demonstrated the best electrochemical characteristics, delivering a high specific capacitance of 507.42 F/g in a three-electrode setup. It also achieved an energy density of 22.89 Wh/kg and a power density of 584.61 W/kg, outperforming its 2CY, 4CY, and 5CY counterparts. Notably, the 3CY electrode exhibited the lowest series resistance (1.59 Ω), indicative of enhanced charge transport and minimal internal resistance. When integrated into an ASC device (NiSe-3CY//activated carbon), it maintained a specific capacitance of 18.78 F/g, with an energy density of 8.45 Wh/kg and power density of 385.03 W/kg. Furthermore, the device exhibited impressive areal and volumetric capacitances of 351 mF/cm² and 1.09 F/cm³, respectively, with a corresponding volumetric energy density of 0.49 mWh/cm³. Long-term cycling tests revealed excellent durability, retaining 91% of its initial capacity after 10k cycles with a high Coulombic efficiency of 99%. These results confirm that the 3CY electrode is a highly promising candidate for next-generation energy storage systems, offering a balanced combination of high capacitance, energy density, and cycling stability. Full article

Supercapacitors have a better power density than batteries; however, there is room for improvement in energy density. Co₃V₂O₈ nanoparticles were synthesized using the hydrothermal approach, with the reaction duration tuned to enhance energy density. At a 10 h hydrothermal reaction time, bundles of nanowires with void spaces were obtained, demonstrating excellent areal capacitance of 4.67 F/cm², energy density of 94 μWh/cm², and power density of 573 μW/cm² at a current density of 3 mA/cm². With activated carbon (AC) and Co₃V₂O₈ nanoparticles prepared over a 10-h hydrothermal reaction period, an asymmetric supercapacitor (ASC) was assembled. The device performed admirably in terms of energy storage capacity, with an areal capacitance of 781 mF/cm² and a volumetric capacitance of 1.43 F/cm³. The ASC’s cyclic stability demonstrated capacity retention of 83.40% after 5000 cycles. The powering of red LEDs was used to show practical applications. In a 2M KOH electrolyte, the optimized Co₃V₂O₈ electrode demonstrated good electrocatalytic performance for the hydrogen evolution process, with an overpotential of 259 mV at a current density of 10 mA/cm². Overall, water splitting studies revealed a potential of 1.78 V with little potential enhancement after 8 h of Chrono potentiometric stability. As a result, Co₃V₂O₈ nanoparticles prepared at a 10 h hydrothermal reaction time offer excellent electrode materials for energy storage in supercapacitors and electrocatalytic applications for total water splitting. Full article

It is crucial for energy storage devices to construct electrode materials with excellent performance. However, enhancing energy density and cycling stability for supercapacitors is a significant challenge. We successfully synthesized CoNi₂S₄@Ni(OH)₂ nanosheets on the surface of Ni foam substrate by a two-step hydrothermal approach. The obtained products exhibit a remarkable areal capacitance of 1534 F g⁻¹ at a current density of 1 A g⁻¹. Moreover, even after 10,000 cycles, the specific capacitance remains 90% of its initial value, highlighting the exceptional long-term stability and durability. Furthermore, an asymmetric supercapacitor (ASC) device incorporating the CoNi₂S₄@Ni(OH)₂ material shows remarkable electrochemical performance. It delivers an energy density of 58.5 mW h g⁻¹ at a power density of 2700 W kg⁻¹. The outstanding performance mainly arises from the selection of materials, the design of the structure, and the synergistic interaction between the materials. The result suggests that this material holds great potential as an energy storage material. Full article

Achieving high energy density while maintaining high power density and long cycle life in supercapacitors, particularly in supercapatteries (SCs), through a thermally stable, greener ionic liquid approach remains a significant challenge for an advanced energy storage application. In this work, we prepared high conductive and high charge storage capability bimetallic transition metal molybdate [Ag₂Mo₂O₇ (AgM)], synergistic with reduced graphene oxide (rGO) coated on nickel foam (AgM/rGO/NF). The physio-chemical characterization revealed a ball-like cluster morphology wrapped in rGO nanosheets and a spinel-type cubic structure using scanning electron microscopy (FE-SEM) displays and X-ray diffraction (XRD) analyses. Further, the electrochemical performance of AgM/rGO/NF electrode achieved a remarkable specific C_sp value of 573.63 F/g at a current density of 1.0 A/g in 3 M KOH electrolyte. An asymmetric SCs (ASCs) device was fabricated using AgM/rGO/NF as the positive and rGO as the negative electrodes, achieving a wide potential window of 1.3 V. The ASC demonstrated an energy density of 16.71 Wh/kg at a power density of 642.98 W/kg, highlighting AgM/rGO/NF’s potential as an advanced electrode material for energy storage applications. Full article

Redox-active porous organic polymers (POPs) demonstrate significant potential in supercapacitors. However, their intrinsic low electrical conductivity and stacking tendencies often lead to low utilization rates of redox-active sites within their structural units. Herein, polyimide POPs (donated as PMTA) are synthesized in situ on multi-walled carbon nanotubes (MWCNTs) from tetramino-benzoquinone (TABQ) and 1,4,5,8-naphthalene tetracarboxylic dianhydride (PMDA) monomers. The strong π–π stacking interactions drive the PMTA POPs and the MWCNTs together to form a PMTA/MWCNT composite. With the assistance of MWCNTs, the stacking issue and low conductivity of PMTA POPs are well addressed, leading to the obvious activation and enhanced utilization of the redox-active groups in the PMTA POPs. PMTA/MWCNT then achieves a high capacitance of 375.2 F g⁻¹ at 1 A g⁻¹ as compared to the pristine PMTA POPs (5.7 F g⁻¹) and excellent cycling stability of 89.7% after 8000 cycles at 5 A g⁻¹. Cyclic voltammetry (CV) and in situ Fourier-Transform Infrared (FT-IR) results reveal that the electrode reactions involve the reversible structural evolution of carbonyl groups, which are activated to provide rich pseudocapacitance. Asymmetric supercapacitors (ASCs) assembled with PMTA/MWCNTs and activated carbon (AC) offer a high energy density of 15.4 Wh kg⁻¹ at 980.4 W kg⁻¹ and maintain a capacitance retention of 125% after 10,000 cycles at 5 A g⁻¹, indicating their good potential for practical applications. Full article

A flexible asymmetric supercapacitor (ASC) is successfully developed by using the composite of MoO₃ and graphene oxide (GO) electrochemically deposited on carbon cloth (CC) (MoO₃/rGO/CC) as the cathode, the MnO₂ deposited on CC (MnO₂/CC) as the anode, and Na₂SO₄/polyvinyl alcohol (PVA) as the gel electrolyte. The results show that the introduction of the GO layer can remarkably increase the specific capacitance of MoO₃ from 282.7 F g⁻¹ to 341.0 F g⁻¹. Furthermore, the combination of such good electrode materials and a neutral gel electrolyte renders the fabrication of high-performance ASC with a large operating potential difference of 1.6 V in a 0.5 mol L⁻¹ Na₂SO₄ solution of water. Furthermore, the ASCs exhibit excellent cycle ability and the capacitance can maintain 87% of its initial value after 6000 cycles. The fact that a light-emitting diode can be lit up by the ASCs indicates the device’s potential applications as an energy storage device. The encouraging results demonstrate a promising application of the composite of MoO₃ and GO in energy storage devices. Full article

Binary transition metal oxide complexes (BTMOCs) in three-dimensional (3D) layered structures show great promise as electrodes for supercapacitors (SCs) due to their diverse oxidation states, which contribute to high specific capacitance. However, the synthesis of BTMOCs with 3D structures remains challenging yet crucial for their application. In this study, we present a novel approach utilizing a single-step hydrothermal technique to fabricate flower-shaped microspheres composed of a NiCo-based complex. Each microsphere consists of nanosheets with a mesoporous structure, enhancing the specific surface area to 23.66 m² g⁻¹ and facilitating efficient redox reactions. When employed as the working electrode for supercapacitors, the composite exhibits remarkable specific capacitance, achieving 888.8 F g⁻¹ at 1 A g⁻¹. Furthermore, it demonstrates notable electrochemical stability, retaining 52.08% capacitance after 10,000 cycles, and offers a high-power density of 225 W·kg⁻¹, along with an energy density of 25 Wh·kg⁻¹, showcasing its potential for energy storage applications. Additionally, an aqueous asymmetric supercapacitor (ASC) was assembled using NiCo microspheres-based complex and activated carbon (AC). Remarkably, the NiCo microspheres complex/AC configuration delivers a high specific capacitance of 250 F g⁻¹ at 1 A g⁻¹, with a high energy density of 88 Wh kg⁻¹, for a power density of 800 W kg⁻¹. The ASC also exhibits excellent long-term cyclability with 69% retention over 10,000 charge–discharge cycles. Furthermore, a series of two ASC devices demonstrated the capability to power commercial blue LEDs for a duration of at least 40 s. The simplicity of the synthesis process and the exceptional performance exhibited by the developed electrode materials hold considerable promise for applications in energy storage. Full article

This research delves into asymmetric supercapacitor (ASC) design, utilizing activated carbon from bamboo poles (AC) and electrodeposited polyaniline (PANI) on nickel foam (NF) as key active components. The composite electrode formed from AC and PANI exhibited enhanced electrochemical attributes in various electrochemical configurations. The specified ASC, PANI@AC/NF//AC/NF, demonstrated a potential of 1.8 V. Impressively, it reached an areal capacitance measuring 423 mF/cm², coupled with an energy density of 190 µWh/cm² at a power density of 900 µW/cm², and maintained ~82% capacitance after 5000 GCD cycles. Notably, our developed ASC presents outstanding research potential for scholars and scientists. Full article

Surface microstructure modification of metal oxides also improves the electrochemical performance of metal oxide nanoparticles. The present investigation demonstrates how varying the urea molar content during the hydrothermal process altered the surfaces of MnCo₂O₄ nanoparticles. Successive increases of 0.1 M in urea concentration transformed the surface shape of MnCo₂O₄ nanoparticles from flower-like to sheet-like microstructures. Excellent electrochemical performance of MnCo₂O₄ nanoparticles was demonstrated in an aqueous 1 M KOH electrolyte. The improved MnCo₂O₄ nanoparticles have been employed to develop an asymmetric supercapacitor (ASC). The ASC device exhibits an energy density of 13 Wh/kg at a power density of 553 W/kg and a specific capacitance of 29 F g⁻¹ at a current density of 4 mA/cm². The MnCo₂O₄ nanoparticle electrode demonstrates remarkable electrocatalytic activity in both HER and OER. The MnCo₂O₄ electrode shows overpotential for HER and OER at 356 mV and 1.46 V, respectively. The Tafel slopes for HER and OER of the MnCo₂O₄ electrode are 356 mV/dec and 187 mV/dec, respectively. Full article

With the continuous development of green energy, society is increasingly demanding advanced energy storage devices. Manganese-based asymmetric supercapacitors (ASCs) can deliver high energy density while possessing high power density. However, the structural instability hampers the wider application of manganese dioxide in ASCs. A novel MnO₂-based electrode material was designed in this study. We synthesized a MnO₂/carbon cloth electrode, CC@NMO, with NH₄⁺ ion pre-intercalation through a one-step hydrothermal method. The pre-intercalation of NH₄⁺ stabilizes the MnO₂ interlayer structure, expanding the electrode stable working potential window to 0–1.1 V and achieving a remarkable mass specific capacitance of 181.4 F g⁻¹. Furthermore, the ASC device fabricated using the CC@NMO electrode and activated carbon electrode exhibits excellent electrochemical properties. The CC@NMO//AC achieves a high energy density of 63.49 Wh kg⁻¹ and a power density of 949.8 W kg⁻¹. Even after cycling 10,000 times at 10 A g⁻¹, the device retains 81.2% of its capacitance. This work sheds new light on manganese dioxide-based asymmetric supercapacitors and represents a significant contribution for future research on them. Full article

This study reports the facile synthesis of rationally designed composite materials consisting of nitrogen-doped graphene quantum dots (N-GQDs) and MnCO₃/ZnMn₂O₄ (N/MC/ZM) on Ni foam using a simple hydrothermal method to produce high-performance supercapacitor applications. The N/MC/ZM composite was uniformly synthesized on a Ni foam surface with the hierarchical structure of microparticles and nanosheets, and the uniform deposition of N-GQDs on a MC/ZM surface was observed. The incorporation of N-GQDs with MC/ZM provides good conductivity, charge transfer, and electrolyte diffusion for a better electrochemical performance. The N/MC/ZM composite electrode delivered a high specific capacitance of 960.6 F·g⁻¹ at 1 A·g⁻¹, low internal resistance, and remarkable cycling stability over 10,000 charge–discharge cycles. Additionally, an all-flexible solid-state asymmetric supercapacitor (ASC) device was fabricated using the N/MC/ZM composite electrode. The fabricated ASC device produced a maximum energy density of 58.4 Wh·kg⁻¹ at a power density of 800 W·kg⁻¹ and showed a stable capacitive performance while being bent, with good mechanical stability. These results provide a promising and effective strategy for developing supercapacitor electrodes with a high areal capacitance and high energy density. Full article

Transition metal sulfides (TMSs) are considered as attractive materials in the areas of energy storage because of their unique redox properties, excellent electronic conductivity, as well as environmental friendliness. However, poor cyclic stability and limited electrochemical active sites hinder their further application. To address this issue, a flower-like hierarchical CuCo₂S₄ structure is constructed by a two-step hydrothermal method. In this nanostructure, CuCo₂S₄ grows outward to form a tightly bound hierarchical structure on the nickel foams (NFs). This oriented structure can provide more laminar gaps for electrolyte ion diffusion, exposing more reaction sites to increase the ion transport efficiency between the layers, reducing the ion transport resistance and improving the reaction kinetics. Thus, the CuCo₂S₄ electrode exhibits excellent energy storage performance, exhibiting a high specific capacity of 1415.6 F g⁻¹ at 1 A g⁻¹. After 10,000 cycles of 10 A g⁻¹, it still has 91.9% of the initial performance. In addition, an asymmetrical supercapacitor (ASC) was constructed by choosing CuCo₂S₄ as the anode and RGO as the cathode, which has the maximum energy density (61.8 Wh Kg⁻¹) at 812.1 W Kg⁻¹ and significant cycling endurance (92.05% retention) at 10,000 turns. Briefly, the researchers successfully constructed an array of CuCo₂S₄ flower-like hierarchical nanostructures and confirmed their potential application in supercapacitors. Full article

In this work, a series of urchin-like Ce(HCOO)₃ nanoclusters were synthesized via a facile and scalable microwave-assisted method by varying the irradiation time, and the structure–property relationship was investigated. The optimization of the reaction time was performed based on structural characterizations and electrochemical performances, and the Ce(HCOO)₃-210 s sample shows a specific capacitance as high as 132 F g⁻¹ at a current density of 1 A g⁻¹. This is due to the optimal mesoporous hierarchical structure and crystallinity that are beneficial to its conductivity, offering abundant Ce³⁺/Ce⁴⁺ active sites and facilitating the transportation of electrolyte ions. Moreover, an asymmetric supercapacitor based on Ce(HCOO)₃//AC was fabricated, which delivers a maximum energy density of 14.78 Wh kg⁻¹ and a considerably high power density of 15,168 W kg⁻¹. After 10,000 continuous charge–discharge cycles at 3 A g⁻¹, the ASC device retains 81.3% of its initial specific capacitance. The excellent comprehensive electrochemical performance of this urchin-like Ce(HCOO)₃ offers significant promise for practical supercapacitor applications. Full article