Electrochemical Performance For Supercapacitors Research Articles

Functionalization Strategies of Iron Sulfides for High-Performance Supercapacitors

AbstractSupercapacitors have emerged as a promising class of energy storage technologies, renowned for their impressive specific capacities and reliable cycling performance. These attributes are increasingly significant amid the growing environmental challenges stemming from rapid global economic growth and increased fossil fuel consumption. The electrochemical performance of supercapacitors largely depends on the properties of the electrode materials used. Among these, iron-based sulfide (IBS) materials have attracted significant attention for use as anode materials owing to their high specific capacity, eco-friendliness, and cost-effectiveness. Despite these advantages, IBS electrode materials often face challenges such as poor electrical conductivity, compromised chemical stability, and large volume changes during charge–discharge cycles. This review article comprehensively examines recent research efforts aiming at improving the performance of IBS materials, focusing on three main approaches: nanostructure design (including 0D nanoparticles, 1D nanowires, 2D nanosheets, and 3D structures), composite development (including carbonaceous materials, metal compounds, and polymers), and material defect engineering (through doping and vacancy introduction). The article sheds light on novel concepts and methodologies designed to address the inherent limitations of IBS electrode materials in supercapacitors. These conceptual frameworks and strategic interventions are expected to be applied to other nanomaterials, driving advancements in electrochemical energy conversion.

Ce-doped NiFe-layered-double-hydroxide hierarchical nanocomposite and metal/imidazolate framework carbon nanotube nanocomposite: A bifunctional material for OER electrocatalyst and supercapacitor electrode applications

The development of nanocomposites as electrocatalysts with low cost and high efficiency for OER and as electrode material enhancing the electrochemical performance of supercapacitors are the most popular investigations in this field. Herein, a new bifunctional composite including Ce-doped NiFe-LDH Nanosheets and ZIF-derived carbon base incorporating neodymium and Fe into the structure of Zeolitic Imidazolate Framework is proposed and the construction was through entering Fe-ZIF8@Nd-ZIF67 into the structure of NiFeCe-LDH in different ratios of 10, 20 and 30 %. Various physical and electrochemical tests were conducted to evaluate the nanocomposites. Results indicated that the composite presented a hierarchical porous structure and exhibited outstanding performance for OER and supercapacitor applications. According to the results, the 30 % composite of NiFeCe-LDH/ Fe-ZIF8@Nd-ZIF67 exhibits a superior onset overpotential of 170 mV and an overpotential of 300 mV at a current density of 10 mA·cm−2. Besides, it shows an excellent specific capacitance of 345.36 (F.g−1) at 1 A.g−1. Hence, the synthesized nanocomposite demonstrated outstanding performance in both OER and supercapacitor applications.

Synthesis of Needle-like CoO Nanowires Decorated with Electrospun Carbon Nanofibers for High-Performance Flexible Supercapacitors.

Needle-like CoO nanowires have been successfully synthesized by a facile hydrothermal process on an electrospun carbon nanofibers substrate. The as-prepared sample mesoporous CoO nanowires aligned vertically on the surface of carbon nanofibers and cross-linked with each other, producing loosely porous nanostructures. These hybrid composite electrodes exhibit a high specific capacitance of 1068.3 F g-1 at a scan rate of 5 mV s-1 and a good rate capability of 613.7 F g-1 at a scan rate of 60 mV s-1 in a three-electrode cell. The CoO NWs@CNF//CNT@CNF asymmetric device exhibits remarkable cycling stability and delivers a capacitance of 79.3 F/g with a capacitance retention of 92.1 % after 10,000 cycles. The asymmetric device delivers a high energy density of 37 Wh kg-1 with a power density of 0.8 kW kg-1 and a high power density of 16 kW kg-1 with an energy density of 23 Wh kg-1. This study demonstrated a promising strategy to enhance the electrochemical performance of flexible supercapacitors.

Preparation of microalgae-based carbon materials with Ni(OH)2 doping and their electrochemical performance

Supercapacitors are a new type of energy storage devices with many advantages. In this study a novel composite material named NiC were synthesized to improved their electrochemical performance in supercapacitors. It was composite of Ni(OH)2 and microalgae-based N-doped activated carbon materials. Activated carbon material prepared from defatted microalgae was excellent electrode material because of their nitrogen-rich characterization and porous structure. The Ni(OH)2 as a metallic material could provide considerable pseudo-capacitance for capacitors. In this study, Ni(OH)2 was successfully doped into carbon materials using a hydrothermal method at a temperature of 150 °C for 4 h. The flower-like structure of metallic materials was observed in SEM images and two forms of elemental Ni ions (Ni3+ and Ni2+) were detected in XPS. The porosity of the composite materials NiC was retained to some extent (specific surface area of 502 m2/g for sample NiC10). Moreover, the specific capacitance value of composite material NiC20 was increased by 190 % compared to its parent carbon material, indicating that the capacitive performance of the composite materials was significantly improved. The capacitance retention of NiC20//NiC20 in a two-electrode system was up to 75.29 % over 5000 cycles. This research will provide necessary information for high-performance electrochemical materials based on microalgae-based carbon materials.

Efficient hybrid supercapacitor performance enabled by large surface area of 2D mesoporous zinc sulfide nano-sheets synthesized via microwaves

Researchers have shown a significant amount of interest in synthesizing high energy density supercapacitors using a simplest, fast, and low cost technique. The electrochemical performance of supercapacitors can be impacted by the surface area and morphology of electrode materials. A one-step, rapid, and economical microwave-assisted synthesis technique was employed in this study in order to prepare mesoporous nanosheets that are composed of zinc sulfide. The ZnS-based nanosheets possess a large surface area of ∼120 m2g−1 and a mesoporous structure of a pore diameter of <22 nm, which offers numerous electrochemical active sites and it facilitates an excellent super capacitive performance, which is due to its shortened ion/electron diffusion path. The prepared mesoporous nanosheets exhibit a higher specific capacitance of 2282 Fg−1 (1037 C/g) when subjected to a 1 Ag−1 in 2 M KOH aqueous electrolyte with high capability rate. The fabricated device exhibits a high specific capacitance of 252.5 Fg−1 (140 C/g) at 1 Ag−1, which produces a remarkable energy density of about 90 Whkg−1 at 800 Wkg−1 value of power density and an excellent retention of ∼95 % after 10,000 cycles at 6 Ag−1. This study designed an instant, straightforward and low-cost approach to fabricate ZnS nanosheet electrode materials that exhibit excellent performance for supercapacitor applications.

Cellulose-based water-in-salt ZnBr2 hydrogels with multiple functions for energy storage devices

A new simple preparation method for water-in-salt-type cellulose hydrogels filled with ZnBr2 is reported. The ZnBr2 hydrogel electrolyte can be applied to zinc-ion hybrid supercapacitors and Zn-Br interfacial batteries. The water-in-salt ZnBr2 hydrogel serves as a stable electrolyte for good electrochemical performance in zinc-ion hybrid supercapacitors without redox reactions and can participate in the charging/discharging process of the Zn‒Br interfacial battery through the redox reaction of halogen anions. The assembled zinc-ion hybrid supercapacitor exhibits a specific capacitance of 241.8 F g-1 at 0.5 A g-1. Furthermore, after a 10000-cycle-long charging/discharging test at 5 A g-1, the coulombic efficiency is found at nearly 100%. The interfacial battery reaches the highest energy efficiency of 66% at a current density of 3 mA cm-2 at 0–1.8 V and displays a good cycle life with an 88% average coulombic efficiency at 3 mA cm-2. This work expands the application of hydrogels and provides new possibilities for optimizing the high performance of electrolytes.

One-pot synthesis of hydroxypropyl methylcellulose-based gel polymer electrolytes for high-performance supercapacitors

The electrolyte is a crucial component that significantly affects the electrochemical performance of supercapacitors. The hydroxypropyl methylcellulose (HPMC)-based gel polymer electrolyte (GPE) with high operating voltage was synthesized via an innovative “one-pot” method in this study, and the impacts of organic solvent/water ratio and LiNO3 concentration on gelation and conductivity of the GPE were investigated systematically. Under the optimal condition with a DMF/water ratio of 10:0 and the incorporation of 7 % LiNO3, the ionic conductivity reached 1.06 S m−1. Integrated into symmetric supercapacitors, the HPMC-based GPE demonstrated an expanded electrochemical window of 2.7 V. It also possessed a specific capacitance of 115.8 F g−1 at 1.0 A g−1, an energy density of 29.31 Wh kg−1, and outstanding cyclic stability, retaining 86 % of its initial capacitance after 2000 cycles. Through cyclic stability tests under pressure conditions, the assembled flexible supercapacitors were able to maintain capacitance retention of 60 % and coulombic efficiency of 97 %. This work offers a streamlined synthesis for HPMC-based GPE with superior electrochemical properties, which exhibits its potential in advancing supercapacitor technology for flexible electronics.

Synthesis and Characterization of Synergetic Pd/MoO3–rGO Hybrid Material as Efficient Electrode for Supercapacitor Application

In this work, study synthesized Pd–rGO and Pd/MoO3–rGO nanocomposites via a one-pot hydrothermal method, serving as efficient electrodes for supercapacitor applications. Various analytical techniques, including XRD, XPS, HRTEM, BET, and Raman spectroscopy, were employed to characterize the structural, morphological, and physiochemical properties to assess the electrochemical supercapacitor performance of nanocomposite materials. The analyses confirmed that the charge transfer mechanism between the MoO3-NR with Pd-rGO in Pd/MoO3–rGO samples has significantly improved the electrochemical performance of Pd/MoO3–rGO by 2.7 times compared to Pd-rGO sample (105.00 F/g at 0.5 A/g). Remarkably, the Pd/MoO3–rGO hybrid material exhibited excellent electrochemical activity, boosting a specific capacitance of 291.50 F/g at a current density of 0.5 A/g, accompanied by energy density and power density values of 18.06 Wh/kg and 250.00 W/kg, respectively. Furthermore, it demonstrated noteworthy stability over prolonged usage, retaining 88.46% of its capacity after 1,000 cycles at a constant current density of 1.0 A/g. These findings underscore the promising potential of the Pd/MoO3–rGO nanocomposite as a highly effective electrode material for supercapacitors.

The Impact of Biowaste Composition and Activated Carbon Structure on the Electrochemical Performance of Supercapacitors.

The increasing demand for sustainable and efficient energy storage materials has led to significant research into utilizing waste biomass for producing activated carbons. This study investigates the impact of the structural properties of activated carbons derived from various lignocellulosic biomasses-barley straw, wheat straw, and wheat bran-on the electrochemical performance of supercapacitors. The Fourier Transform Infrared (FTIR) spectroscopy analysis reveals the presence of key functional groups and their transformations during carbonization and activation processes. The Raman spectra provide detailed insights into the structural features and defects in the carbon materials. The electrochemical tests indicate that the activated carbon's specific capacitance and energy density are influenced by the biomass source. It is shown that the wheat-bran-based electrodes exhibit the highest performance. This research demonstrates the potential of waste-biomass-derived activated carbons as high-performance materials for energy storage applications, contributing to sustainable and efficient supercapacitor development.

Synergistic effects of MXene and Co3O4 in composite electrodes: High-performance energy storage solutions

The development of high-performance electrode materials is crucial for advancing supercapacitor technology. The two-dimensional layered structure of MXene (Ti3C2Tx) presents high conductivity, abundant surface functional groups and accessible ion interaction between layers. However, the MXene suffers from the layer aggregation. To overcome this issue, we synthesized a composite material combining MXene with cobalt oxide (Co3O4) to enhance electrochemical performance in supercapacitors. MXene’s two-dimensional layered structure, high conductivity, and abundant surface functional groups allow for efficient ion intercalation, while Co3O4 contributes high theoretical capacitance and rich oxidation states. The resulted MXene/Co3O4 composite exhibits an impressive areal capacitance of 6.456F/cm2 at a current density of 3 mA/cm2, maintaining 90.52 % capacitance retention at 30 mA/cm2, and 81.37 % capacity after 5000 charge–discharge cycles. Additionally, the asymmetric supercapacitor (ASC) device fabricated using the MXene/Co3O4 composite achieves a power density of 6.41 mW/cm2 at an energy density of 0.37 mWh/cm2, with 82.3 % capacitance retention after 5000 cycles. These results demonstrate that the MXene/Co3O4 composite material is a promising candidate for high-performance supercapacitors, offering significant improvements in rate capability and long-term cycling stability.

Ultrafast Synthesis of MXenes in Minutes via Low-Temperature Molten Salt Etching.

Developing green and efficient preparation strategies is a persistent pursuit in the field of 2D transition metal nitrides and/or carbides (MXenes). Traditional etching methods, such as HF-based or high-temperature Lewis-acid-molten-salt etching route, require harsher etching conditions and exhibit lower preparation efficiency with limited scalability, severely constraining their commercial production and practical application. Here, an ultrafast low-temperature molten salt (LTMS) etching method is presented for the large-scale synthesis of diverse MXenes within minutes by employing NH4HF2 as the etchant. The increased thermal motion and improved diffusion of molten NH4HF2 molecules significantly expedite the etching process of MAX phases, thus achieving the preparation of Ti3C2Tx MXene in just 5minutes. The universality of the LTMS method renders it a valuable approach for the rapid synthesis of various MXenes, including V4C3Tx, Nb4C3Tx, Mo2TiC2Tx, and Mo2CTx. The LTMS method is easy to scale up and can yield more than 100g Ti3C2Tx in a single reaction. The obtained LTMS-MXene exhibits excellent electrochemical performance for supercapacitors, evidently proving the effectiveness of the LTMS method. This work provides an ultrafast, universal, and scalable LTMS etching method for the large-scale commercial production of MXenes.

Multi-level nanostructures of NiCoP/CNTs/CuO nanowire arrays/Cu foam with excellent electrochemical performance for flexible supercapacitors

Transition metal phosphides (TMPs) have gained significant attention as promising electrode materials for supercapacitors due to their quasi-metallic properties, high electrical conductivity, and rapid redox reactions. Despite these advantages, their electrochemical performance is often hindered by low ion and electron transfer rates, as well as suboptimal cycling stability. To overcome these challenges, we have developed a novel composite electrode material by in-situ growth of Cu(OH)₂ nanowire arrays on copper foam, which acts as a robust scaffold for carbon nanotubes (CNTs) and NiCo-layered double hydroxides (NiCo-LDH). Following a phosphating process, we fabricated a core-shell structured NiCoP/CNTs/CuO nanowire array on copper foam (NiCoP/CNTs/CuO NWAs/Cu foam) with a multistage nanoarchitecture. This design features intrinsic nano-organization, low inherent resistance, short electron transport pathways, and stable electrochemical properties. In a 3 M KOH solution, the flexible NiCoP/CNTs/CuO NWAs/Cu Foam electrode achieved an impressive specific area capacitance of 15.88 F cm⁻². The assembled flexible asymmetric devices achieve an area-specific capacitance of 4718.04 mF cm⁻², an energy density of 29.79 mWh cm⁻³, and a power density of 4170.96 mW cm⁻³ at a working voltage of 1.8 V. Furthermore, after 10,000 charge-discharge cycles, the electrode retained 89.18 % of its initial capacity. This synthesis strategy for hierarchical nanostructured materials provides valuable insights for the development of next-generation materials in the field of flexible supercapacitors.

Harnessing the potential of Type-II heterostructures: NiO/TiO2/ZnO fibers for enhanced photocatalytic and electrochemical performance in asymmetric supercapacitors

A novel two-step approach, electrospinning followed by wet chemical route, was used for the synthesis of NiO/TiO2/ZnO heterostructure fibers. Structural, morphological, and elemental analyses confirmed the single-phase formation with a unique, one-dimensional furry insect-like morphology, free of impurities. BET analysis revealed a significant increase in the specific surface area from 12.64 to 54.50 m2/g for NiO/TiO2/ZnO heterostructure fibers, indicating the existence of more active sites for catalytic and redox activities. Optical studies demonstrated a reduction in the band gap of NiO in the presence of TiO2 and ZnO, enhancing the photocatalytic properties. The Langmuir-Hinshelwood kinetic model was employed to measure the reaction rate constant, showing improved photocatalytic performance of NiO by enhancing the separation rate of photo-generated electrons and holes on its surface. Furthermore, the electrochemical performance of the prepared fibers-based asymmetric supercapacitors (ASCs) showed a low polarization, attributed to low charge transfer resistance. The NiO/TiO2/ZnO fibers-based ASCs exhibited higher specific capacitance (108 F/g), with a maximum specific energy density of 9.6 Wh/kg at a specific power density of 2000 W/kg indicating excellent performance suitable for finding potential uses in energy storage applications. Various practical and physical tests further certified the efficient performance of the prepared NiO/TiO2/ZnO heterostructure fibers-based asymmetric supercapacitors. The contribution of NiO and TiO2 to the inner surface were ∼52.02 and ∼47.08 %, respectively. In contrast, the NiO/TiO2/ZnO fibers showed a notable difference, with ZnO-NWs contributing ∼4.99 % to the overall surface. This increase in the inner surface contribution to around 95.01 % indicates that the growth of ZnO-NWs provides additional channels for electrochemical reactions during redox processes and enhances adhesion between the ZnO-NWs and NiO/TiO2 heterostructure, facilitating OH− ions transportation.

Microstructural Regulation of Co TCPP by Acetylene Black: Enhanced Electrochemical Performance for Wearable Supercapacitors

Abstract With the rapid development of wearable devices, flexible supercapacitors have become an important energy storage prototype due to their inherent flexibility and high power density. Two-dimensional metal-organic framework (2D MOF) nanosheets are widely used in energy storage systems due to their structural tunability and anisotropy. However, their high surface energy tends to lead to aggregation, which results in poor dispersion and rheology of formulated inks and inhomogeneity of printed electrodes. Existing methods involve surface modulation by capped organic ligands, yet ignore the inherent conductivity and stability of MOFs. To overcome the low conductivity and aggregation problems of 2D MOFs, we adopted a novel approach combining mechanical intercalation and surface functionalization of cobalt-based porphyrin frameworks (Co TCPP) with acetylene black (AB). The unique microstructure of the composite material leads to favorable changes in the electronic properties of AB, which reduces the overall internal resistance and promotes rapid charge transfer. For this purpose, we have prepared micro-supercapacitors (MSCs) using dispensing printing technology. This integrated material has excellent mechanical flexibility and maintains 92% specific capacitance even under extreme bending and torsion. This study highlights the potential of integrating 2D MOFs with carbon-based materials (e.g., acetylene black) for a variety of applications in wearable electronics, and provides a guiding scheme for future micro-modulation of 2D MOFs using conductive materials.

Influence of Phosphoric Acid Activation on Physiochemical Characteristics of Activated Carbons and Their Performance as Supercapacitor

ABSTRACTWe investigate the influence of phosphoric acid (H3PO4) activation on physiochemical characteristics of activated carbons (ACs) as a function of number of activation steps such as two‐step and three‐step and impregnation ratio (IR). Scanning electron microscopy observations identified that different morphologies in the forms of graphene sheet‐like, nano‐granular, and flake‐like carbon structure in the cases of ACs. FTIR spectroscopy confirmed that successful incorporation of phosphorous group in the ACs by H3PO4 activation. X‐ray diffraction (XRD) profile exposed that irrespective of the activation method and IR, all AC samples showed narrow and sharp XRD crystalline peak along with the amorphous signals. Raman scattering analysis suggested that three‐step activation create more defective structure as compared to two‐step activation route. Nitrogen adsorption–desorption isotherm measurements indicated that upon fabricating ACs via three‐step and two‐step activation approach, around 6.5 times and 3‐fold enhancement in the value of surface area of ACs as compared to that of carbon before activation. In addition, higher the IR value, lower the textural properties of ACs. This study demonstrated that three‐step activation methodology is capable of generating highly porous AC when compared to two‐step activation route. Cyclic voltammetry analysis showed that for the electrode developed from AC that fabricated via three‐step activation, capacitance retention of 50% is achieved upon tuning the scan rate by 10 times. The same electrode exhibited the capacitance retention of 45% upon increasing the current density by 10 times. We have also compared the electrochemical performance of symmetric and asymmetric supercapacitors. Electrochemical capacitance retention of symmetric and asymmetric supercapacitors is determined to be 100% and 92% respectively after 1000 cycles at the current density of 1 A g−1. Based on the Ragone plot study, it is observed that the maximum energy density of 5 W h kg−1 and the maximum power density of 943 W kg−1 are attained for the case of symmetric supercapacitors. Asymmetric supercapacitor displayed improved energy density of 7.15 W h kg−1 and modest power density of 432 W kg−1.

Impressive electrochemical characteristics of freeze-dried nanosheet structured Mn2P2O7 for affordable electrochemical capacitor

The electrochemical capacitive performance of supercapacitors (SCs) is mainly evaluated by active electrode material, which plays a critical participation. At present, transitional metallic pyrophosphates (TMPs) have grabbed more interest as active electrodes in SC configuration. In this work scenario, we informed a novel strategic synthesis route for constructing Mn2P2O7 (MP) through an ultrasonic probe-assisted chemical reaction approach. The electrode in the form of a monoclinic, freeze-dried nanosheet structure characterized by XRD, FESEM- TEM, and its signature chemical bonds and chemical composition were confirmed via FTIR and EDS analysis, respectively. As prepared active sample was successfully sent into electrochemical investigation tools such as Cyclic Voltagrams (CV), Galvanostatic charge/discharge (GCD), electrochemical impedance analysis (EIS), and Cycling life span (stability) using three and two-electrode set-up. These tests indicate that the active sample holds an impressive capacitive value of 558 F/g at scanning range of 2 mV/s, a specific capacity of 420 C/g at 1 A g-1, magnificent rate capability, 90 % retention over 10,000 successive voltammograms in three-electrode measurements. Additionally, the fabricated symmetric supercapacitor device shows superior energy density, power density, and good rate capability in two electrode investigations. The mentioned prominent results reflect that engineered MP and its characteristics are the efficient fruits in manufacturing affordable electrochemical capacitors.

Advancements in lithium zinc phosphate (LZP) nanoparticles: Enhanced electrochemical performance for high-efficiency supercapacitors

The synthesized LiZnPO4 nanoparticles were characterized at different temperatures like (400oC, 500 °C, 600 °C, and 700 °C) using various techniques including XRD, FTIR, FESEM, XPS, and electrochemical analyses. X-ray diffraction (XRD) analysis of LiZnPO4 nanoparticles sintered at temperatures from 400 to 700 °C revealed well-crystallized structures at 700 °C, with preferred orientations along (202) and (020) planes. The Scherrer formula was employed to determine crystallite sizes, showing an increase from 55 nm at 400 °C to 85 nm at 700 °C. The annealing temperature influences the formation of microspherical aggregates, determining their surface area and thereby affecting energy storage performance. Samples annealed at 700 °C exhibited a specific capacitance of approximately 268 F/g at a current density of 0.5 A/g and scan rate of 5 mV/s. Our studies indicate that LiZnPO4-based nanostructures have substantial potential for the development of hybrid supercapacitors.

Butanedioic acid unlock shelf-stable Ti3C2Tx (MXene) dispersions and their electrochemical performance in supercapacitor

MXene experiences significant oxidation and gradual deterioration in aqueous media due to its inadequate chemical stability, which hinders its further advancement. This study presents a simple and effective approach to prevent the degradation of Ti3C2Tx MXene nanosheets in aqueous media by chemically encapsulating with butanedioic acid (succinic acid (SSA)). Specifically, the impact of pH and antioxidant content on the rate of oxidation of Ti3C2Tx is investigated together with their electrochemical behavior at different intervals. The research demonstrates that the oxidation rate of MXene must be prevented at a suitable concentration of antioxidants; higher doses of antioxidants cause aggregation, while lower concentrations accelerate the oxidation process. Furthermore, fluctuations in pH levels within the dispersion indicate that under acidic conditions, MXene experiences a greater level of oxidation as a result of elevated proton reactivity, which ultimately leads to material degradation. On the other hand, alkaline environments tend to reduce oxidative reactions, leading to increased stability of MXene. Consequently, MXene-SSA can demonstrate long-term stability in water for up to 35 weeks. The electrochemical properties of SSA-encapsulated MXene sheets are assessed as a supercapacitor electrode throughout a time gradient. In comparison to fresh MXene (299 F g−1 at 1 A g−1), the specific capacitances of SSA-protected MXene (321 F g−1 at 1 A g−1) remain unchanged after a long time. Based on DFT calculations, it has been observed that succinic acid creates beneficial hydrogen bonding interactions with Ti sites that possess a lower coordination number, hence improving the stability of Ti3C2Tx.

Green Power: The Role of Plant-Based Biochar in Advanced Energy Storage.

This comprehensive review aims to provide an overview of recent progress in utilizing plant-based biochar for supercapacitors. It specifically focuses on biochar derived from plant biomass such as agricultural residues, weeds and aquatic plants, examining their potential in energy storage applications. It explores various synthesis methods like pyrolysis and hydrothermal carbonization and evaluates their impact on biochar's structure and electrochemical properties. Additionally, it examines the electrochemical performance of biochar-based supercapacitors, focusing on parameters such as capacitance, cycling stability, and rate capability. Strategies to enhance biochar's electrochemical performance, such as surface modification and composite fabrication, are also discussed. Furthermore, it addresses existing challenges and prospects in harnessing plant-based biochar for supercapacitor applications, highlighting its potential as a sustainable and efficient electrode material for next-generation energy storage devices.

Vacancy Engineering of Selenium-Vacant NiCo2Se4 with Enhanced Electrochemical Performance for Supercapacitor.

Vacancy engineering effectively modulates the electronic properties of electrode materials, thereby improving their electrochemical performance. In this study, we prepared selenium-deficient NiCo2Se4 (Sev-NCS) using ethylene glycol as a reducing agent in NaOH alkaline environment, and investigated its potential as an electrode material for supercapacitors. Both theoretical and experimental results confirmed that the introduction of vacancies altered the morphology and electronic structure of NiCo2Se4, which in turn synergistically improved the conductivity and the diffusion capability of electrolyte ions. The optimized Sev-NCS electrode achieved an excellent specific capacitance of 2962.7 F g-1 at a current density of 1 A g-1 and superior cycling stability with a capacitance retention of 89.5% even after 10,000 cycles. Furthermore, an asymmetric device composed of the optimized Sev-NCS electrode as the positive electrode and activated carbon as the negative electrode achieved an energy density of 55.6 Wh kg-1 at a power density of 800 W kg-1. Therefore, this work offers novel insights into the role of vacancy engineering in improving the performance of transition metal compound-based electrode materials for supercapacitor.