Electrochemical Energy Storage Performance Research Articles

Surface-modified composites of metal–organic framework and wood-derived carbon for high-performance supercapacitors

The renewable nature, high carbon content, and unique hierarchical structure of wood-derived carbon make it an optimal self-supporting electrode for energy storage. However, the limitations in specific surface area and electrical conductivity defects pose challenges to achieving satisfactory charge storage in wood-derived carbon electrodes. Therefore, exploring diverse and effective surface strategies is crucial for enhancing the electrochemical energy storage performance. Herein, a decoration technique for enhancing aesthetic appeal involves applying a metal–organic framework (Ni/Co-MOF) containing nickel and cobalt onto the inner walls of wood tracheids. The sequential modification steps include carbonization, oxidation activation, and acid-etching. The Ni/NiO/CoO-CW-4 electrode, made by acid-etching carbonized wood (CW) doped with nickel, nickel oxide, and cobalt oxide for 4 h, has excellent surface area and pore size distribution, high graphitization degree, and exceptional conductivity. Furthermore, surface modification optimizes the surface chemistry and phase composition, resulting in a 0.8 mm thick Ni/NiO/CoO-CW-4 electrode with an exceptionally high areal capacitance of 16.76 F cm−2 at 5 mA cm−2. Meanwhile, the fabricated solid-state supercapacitor achieves an impressive energy density of 0.67 mWh cm−2 (8.38 mWh cm−3) at 2.5 mW cm−2 (31.25 mW cm−3), surpassing representative modified wood-based carbon electrodes by approximately 2–7 times. Additionally, the supercapacitor demonstrates exceptional stability, maintaining 96.21 % of capacitance even over 10,000 cycles. The parameters presented here demonstrate a significant improvement compared to those typically observed in most modified wood-derived carbon-based supercapacitors, effectively addressing common issues of low energy density and suboptimal cycling performance with wood carbon composites.

Synthesis of rice husk derived porous carbon as low-cost and high-performance electrode material for supercapacitors

Porous carbon electrode materials derived from agricultural by-products of food processing have attracted widespread interest. Rice husk (RH) is a promising raw material owing to its abundance and low price. In this study, a supercapacitor electrode was prepared by using recycled RH and secondarily activated with ZnCl2 to enhance its electrochemical energy storage performance. RH carbonized at the optimum temperature (i.e., 800 °C) was activated to synthesize RH-800-X (X = 1, 2, 3, 4, or 5, representing the mass ratio of ZnCl2 to RH-800). Sample RH-800-3 exhibited the highest specific surface area (1348.29 m2 g−1) and mesoporous pore volume (0.8375 cm3 g−1) among the samples. In a three-electrode system, the prepared electrodes delivered a high specific capacitance (242 F g−1 at 0.3 A g−1 in 6 M KOH solution). Furthermore, the capacitance retention of RH-800-3 remained at 99.9 % after 17,000 charge/discharge cycles. The results demonstrate the excellent capacitive behavior and superior electrochemical performance of RH-800-3. In addition, symmetrical capacitors prepared using RH-800-3 have an energy density of up to 101 Wh kg−1 at a power density of 900 W kg−1. Therefore, this study presents a simple and effective method for preparing a high-performance electrode material from biomass-derived porous carbon (i.e., recycled RH) and offers a new perspective for the efficient utilization of waste biomass resources.

Silicon Nanowires via Metal-Assisted Chemical Etching for Energy Storage Applications.

Silicon nanowires (SiNWs) have demonstrated great potential for energy storage due to their exceptional electrical conductivity, large surface area, and wide compositional range. Metal-assisted chemical etching (MACE) is a widely used top-down technique for fabricating silicon micro/nanostructures. SiNWs fabricated by MACE exhibit significant surface areas and diverse surface chemistry. Since the material composition and surface chemistry have a significant impact on the electrochemical energy storage performance, integrating SiNWs with diverse materials like porous carbon, metal oxides/sulfides, and polymers, can establish composites with excellent properties. Hence, it is imperative to meticulously fabricate SiNW-based materials with customizable morphologies and enhanced electrochemical energy-storage performance. This review provides an in-depth study of recent advancements in SiNW-based materials with enhanced performance for energy storage systems, such as supercapacitors (SCs) and lithium-ion batteries (LIBs). It includes a concise overview of the history, MACE synthesis, and characteristics of SiNWs. Further, it also explores the key elements that influence the MACE process of SiNWs and delves into structural engineering. Additionally, we introduce recent advances in SiNW-based materials for the design of high-performance energy-storage devices, namely SCs and LIBs. Finally, we present the crucial future prospects of SiNW-based materials for energy-storage applications.

Nanocarbons-Based Trifunctional Electrocatalysts for Overall Water Splitting and Metal-Air Batteries: Metal-Free and Hybrid Electrocatalysts.

Trifunctional electrocatalysts, an exciting class of materials that can simultaneously catalyze hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), can significantly enhance the performance and economic viability of electrochemical energy storage and conversion technologies such as water-splitting electrolyzers, metal-air batteries, fuel cells and their integrated devices. Such multifunctional electrocatalysts encompass multiple active sites that can simultaneously catalyze two or more different electrochemical reactions and are feasible routes for addressing global energy and environmental challenges. This review accounts for nanocarbons-based trifunctional electrocatalysts reported for electrolyzers, metal-air batteries and integrated electrolyzer-battery systems, providing a practical perspective. Metal-free and hybrid (hybrids of nanocarbons and transition metals/compounds) trifunctional electrocatalysts are covered. Given the growing importance of green technologies, we discuss biomass-derived carbon-based trifunctional electrocatalysts separately. The collective information provided in the review could help researchers derive more effective and durable trifunctional electrocatalysts suitable for commercial use.

Multicomponent hierarchical Cu-based advanced cathode for ultrahigh capacity rechargeable Cu-Zn battery

Rechargeable aqueous Zn-based batteries (RAZBs) have emerged as a practically attractive option for large-scale energy storage applications due to their cost-effectiveness, safety, eco-friendliness, and high theoretical capacity. Nonetheless, the application of RAZBs at the grid scale is restricted by the drawbacks of cathode that exhibit low capacities and poor durability. In this work, a multicomponent hierarchical Cu@CuO@Cu2O cathode with superior electrochemical energy storage performance has been successfully synthesized by a fairly simple calcination method. Benefiting from its large active area, fast ion diffusion channel, high conductivity, and synergetic effect between different components, the resulting Cu@CuO@Cu2O electrode exhibits ultrahigh specific capacity (40.2 mAh cm−2, 402 mAh cm−3 at 10 mA cm−2), excellent rate capability (24.8 mAh cm−2, 248 mAh cm−3 at 100 mA cm−2) and satisfactory cycling durability (71.5 % capacity retention after 3800 cycles). To our knowledge, such high areal/volumetric specific capacity ranks top among previously reported Cu-based electrode and other aqueous electrodes. Furthermore, the fabricated Cu@CuO@Cu2O//Zn battery achieves an extraordinary energy density of 24.5 mWh cm−2 and a remarkable cyclic capability of 91 % capacity retention after 3000 cycles, highlighting its potential for large-scale energy storage in RAZBs.

Unveiling the Versatile Applications of Cobalt Oxide-Embedded Nitrogen-Doped Porous Graphene for Enhanced Energy Storage and Simultaneous Determination of Ascorbic Acid, Dopamine and Uric Acid

The advancement of electrode materials is essential for addressing the energy and biomedical challenges. A multi-functional approach was employed to create a new electrode material of cobalt oxide-embedded nitrogen-doped porous graphene (Co3O4@NpG) for sensing and energy storage applications. In the present study, we have fabricated a new electrochemical sensing platform based on Co3O4@NpG. The sensing performance and selective detection capability of the demonstrated sensor was optimized and tested by determining dopamine (DA), uric acid (UA), and ascorbic acid (AA) simultaneously in analyte fortified biological samples. The sensing response is noticed to be linearly dependent upon the concentration of AA, DA, and UA in the range of 0.1–450, 0.1–502, and 0.2–396 μM, respectively. This material also showed good electrochemical energy storage performance when assessed as a supercapacitor electrode. The Co3O4@NpG electrode material showcased a remarkable specific capacitance of 314.58 Fg−1, an energy density of 10.06 Wh kg−1 at a power density of 240 Wkg−1 at 0.5 Ag−1, in a 6 M KOH electrolyte, along with excellent long-term cycling stability. Hence, the material Co3O4@NpG stands out as a promising multifunctional electrode candidate, excelling in the precise simultaneous detection of critical biomolecules besides exhibiting superior energy storage performance.

Growth of Ni-Ga oxalate nanoparticles on 3D current collector as a supercapacitive electrode

Metal oxalate materials have been explored for electrochemical energy storage (EES) applications. Herein, Ni-incorporated gallium oxalate (Ni-Ga-C2O4) based binder-free electrode was fabricated through a facile process. The electrode gathers the benefit of Ni foam contributed as a conductive substrate and also acting as a Ni source with binder-free approach. The Ni-Ga-C2O4 crystalline phase formation was confirmed through X-ray diffraction spectroscopy (XRD). The morphological properties and elemnetal quantification were studied via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron spectroscopy (TEM). Importantly, electrochemical energy storage investigation revealed the Ni-Ga-C2O4 electrode exhibits battery behavior with capacity retention of 85.5 % and possessed the highest specific capacity of 319 C g−1 at 1 A g−1. Overall, the additional contribution of Ni during the synthesis has boosted the physicochemical properties and electrochemical energy storage performance of the Ni-Ga-C2O4 electrode.

Design and fabrication of nitrogen-doped graphene-promoted Na3MnTi(PO4)3@C cathode with three-electron reactions for sodium-ion storage

As a novel cathode material for sodium-ion batteries, Na3MnTi(PO4)3 (denoted as NMTP) has received great attention because of its abundant natural resources, excellent safety, low toxicity as well as three-electron reactions. Unfortunately, the pure NMTP cathode displays a bad conductivity, resulting in an inferior electrochemical performance for sodium energy storage. Herein, we introduce a good route to fabricate the nitrogen-doped graphene-decorated NMTP@C (denoted as NG-NMTP@C) composite with superior rate property and superior cycle stability for the first time. In this fabricated material, the nitrogen-doped graphene nanosheets are dispersed into the NMTP@C particles. Compared to NMTP@C, the prepared NG-NMTP@C cathode possesses better cycle stability and higher capacity. It shows the capacity of 173.1 mAh g−1 at 0.1 C and presents the high capacity retention of around 97.1 % at 10.0 C over 400 cycles. Therefore, this fabricated NG-NMTP@C nanocomposite can be employed as the novel positive electrode in sodium-ion storage.

General synthesis of high-entropy oxides and carbon-supported high-entropy oxides by mechanochemistry.

High-entropy oxides (HEOs) have been receiving a lot of attention due to their excellent properties. However, current common methods for preparing HEOs usually involve high-temperature processes. The development of green synthesis techniques remains an important issue. Carbon-supported HEOs have shown excellent performance in electrochemical energy storage in recent years. Crucially, the traditional methods cannot synthesize carbon-supported HEOs under N2 or air atmospheres. Toward this end, a universal method for preparing carbon-supported HEOs was proposed. During this process, without high-temperature post-treatment, high-entropy LaMnO3 could be synthesized in 2 hours using the mechanical ball-milling method. Furthermore, this method was universal and has been proved in the synthesis of a series of HEOs such as PrVO3, SmVO3, and MgAl2O4. The LaMnO3 species synthesized by this method exhibit excellent catalytic performance in CO combustion and could maintain a conversion rate of over 97% for 350 hours. Subsequently, carbon-supported HEOs could be obtained with 0.5 hours of additional ball-milling, offering significant advantages over traditional methods. This process provides a potential method to synthesize carbon-supported HEOs.

Scalable, Flexible, Magnetic-Field-Guided rULGO Sponge-BN-Cobalt Oxide-Based Supercapacitors: Mechanistic Insights into Multiple Charge Transfer Pathways by the Distribution of Relaxation Times.

Scalable and flexible supercapacitors are in high demand from an application point of view. Through our exploration, we have attained promising performance of electrochemical energy storage under the influence of an external magnetic field for future energy-based applications. In this work, a commercial sponge is used as a template for ultra-large graphene oxide (rULGO) functionalization, followed by the incorporation of Co3O4:BN without the inclusion of binders or conductive additives. The fabricated electrodes, namely, SPG-rULGO and SPG-rULGO-Co3O4:BN, demonstrate superior performance with a potential window of 2.2 V at a magnetic field strength of 13.5 and 28 mT, respectively. A specific capacitance of 218 ± 5% F·g-1 and 312 ± 5% F·g-1, respectively, with retention rates of 80 and 88% over 5000 charge-discharge cycles are achieved. In contrast to the conventional fabrication of the asymmetric device, both electrodes are made using flexible substrates with SPG-rULGO-Co3O4:BN as the positive electrode and SPG-rULGO as the negative electrode eliminating the need to use activated carbon. This configuration yields a specific capacitance of 153 ± 5% F·g-1 at 1 Ag-1, leading to a high energy density of 103 ± 5% W·h·kg-1 at a power density of 1.10 ± 5% kW kg-1 with an 85% retention rate. The charge-discharge mechanism of bare and modified electrodes is probed by the distribution of relaxation time analysis of the coupled electrochemical impedance spectra. The integration of magnetic field with advanced electrode materials opens up other possibilities for optimizing energy storage systems and advancing the field of flexible and mechanically robust supercapacitors.

Nitrogen-rich nanoporous carbon with MXene composite for high-performance Zn-ion hybrid capacitors

The zinc-ion hybrid capacitor, as a novel energy storage system with outstanding electrochemical performance, low cost, and high safety, has attracted widespread research attention. In this work, we report a hetero-structured composite material, C2N@MXene, obtained by alternately stacking porous carbon material C2N with MXene nanosheets. Theoretical calculations and a series of exsitu characterizations reveal that the introduction of MXene nanosheets not only exposes more active sites of C2N, but also significantly enhances the conductivity and stability of the overall composite material, thereby achieving excellent electrochemical energy storage performance. Consequently, as a cathode material for zinc-ion hybrid capacitors, C2N @MXene achieves a high specific capacity of 240 mA h/g at 0.1 A/g and exhibits outstanding rate performance from 1 to 20 A/g. And the capacitance retention rate remains as high as 94%, after 10,000 cycles of charge-discharge at a current density of 5 A/g. Moreover, based on the C2N @MXene electrode, flexible zinc ion micro-capacitor with high area-specific capacity of 264 mF/cm2 was fabricated using laser cutting technology. We believe that this work provides new research strategies for developing high-performance zinc-ion hybrid capacitors.

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.

Separating Cationic and Anionic Redox Activity in the Lithium-Rich Antiperovskite (Li2Fe)SO.

Lithium-rich antiperovskites promise to be a compelling class of high-capacity cathode materials due to the existence of both cationic and anionic redox activity. Little is however known about the effect of separating the electrochemical cationic process from the anionic process and the associated implications on the electrochemical performance. In this context, we report the electrochemical properties of the illustrative example of three different (Li2Fe)SO materials with a focus on separating cationic from anionic effects. With the high-voltage anionic process, an astonishing electrochemical capacity of around 400 mAh g-1 can initially be reached. Our results however identify the anionic process as the cause of poor cycling stability and demonstrate that the fading reported in previous literature is avoided by restricting to only the cationic processes. Following this path, our (Li2Fe)SO-BM500 shows strongly improved performance as indicated by constant electrochemical cycling over 100 cycles at a capacity of around 175 mAh g-1 at 1 C. Our approach also allows us to investigate the electrochemical performance of the bare antiperovskite phase excluding extrinsic activity from initial or cycling-induced impurity phases. Our results underscore that synthesis conditions are a critical determinant of electrochemical performance in lithium-rich antiperovskites, especially with regard to the amount of electrochemical secondary phases, while the particle size has not been found to be a crucial parameter. Overall, separating and understanding the effects of the cationic from the anionic redox activity in lithium-rich antiperovskites provides the route to further improve their performance in electrochemical energy storage.

Green synthesis of nanostructured 1T/2H-MoS2 hybrid phase with polyol solvents and microwave heating

Green synthesis approaches have attracted greatly of attention in recent years since they address the issues associated with sustainability than conventional synthesis methods. New research fields in green nanoscience are being developed as a result of the incorporation of green chemistry principles into nanoscience. In this paper, the successful microwave-assisted green synthesis of MoS2 nanoparticles in a single pot using polyol solvents such as ethylene glycol and glycerol is demonstrated. The coexistence of 1T and 2H phases in MoS2 nanomaterials was determined using advanced techniques such as XRD, Raman, XPS, and TEM images. The highest 1T proportion obtained was 84.5% when compared to the 2H phase. The reaction mechanism and the phase transition between 1T and 2H were described and illustrated. The role of polyol solvents in the practical synthesis of nano MoS2 under microwave heating is also evaluated and explained. Due to the ability of the metallic 1T phase to enhance electrical conductivity, it is believed that hybrid nanostructures exhibit superior electrochemical performance for energy storage and conversion applications.

Enhanced energy storage performance of copper intercalated redox active 1, 2, 4, 5-benzene-tetracarboxylic Acid organic framework

Supercapattery being remarkable energy storage device combining the strength of supercapacitors and batteries can offer both high power and enhanced energy storage capabilities. In the realm of advanced materials, Metal-Organic Frameworks (MOFs) represent a unique category of porous materials formed through strong bonds between organic linkers and metal ions. Through meticulous ingredient selection, MOFs can exhibit extremely large surface areas, exceptional chemical stability, and significant pore volumes. In this study, we demonstrate the electrochemical energy storage performance of copper intercalated MOF (Cu-MOF) synthesized via a hydrothermal method for the application of supercapattery. Initially, we employed a three-electrode assembly to scrutinize the electrochemical characteristics of the synthesized material. To investigate the nature of the electrodes, electrochemical analysis including cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed. The synthesized material exhibited excellent specific capacity of 403.5 C/g at 1.5 A/g, indicating its battery-grade quality. Due to its superior electrochemical performance, the supercapattery device was fabricated by coupling Cu-MOF with activated carbon (AC), Cu-MOF was subjected to positive and AC was employed as the negative electrode. The Cu-MOF//AC exhibited remarkable specific capacity of 165 C/g at 0.7 A/g. Furthermore, this device showcased impressive specific energy of 40 Wh/kg at specific power of 567 W/kg. The device demonstrated an impressive maximum specific power of 6336 W/kg, while its exceptional stability of 95.6 % was demonstrated through 5000 cycles at room temperature. The performance of fabricated device was also evaluated using a theoretical model to assess the diffusive and capacitive contribution. The hybrid characteristics of the devices were investigated using a power law.

CoS2/carbon network flexible film with Co-N bond/π-π interaction enables superior mechanical properties and high-rate sodium ion storage

Flexible electrodes based on conversion-type materials have potential applications in low-cost and high-performance flexible sodium-ion batteries (FSIBs), owing to their high theoretical capacity and appropriate sodiation potential. However, they suffer from flexible electrodes with poor mechanical properties and sluggish reaction kinetics. In this study, freestanding CoS2 nanoparticles coupled with graphene oxides and carbon nanotubes (CoS2/GO/CNTs) flexible films with robust and interconnected architectures were successfully synthesized. CoS2/GO/CNTs flexible film displays high electronic conductivity and superior mechanical properties (average tensile strength of 21.27 MPa and average toughness of 393.18 KJ m−3) owing to the defect bridge for electron transfer and the formation of the π–π interactions between CNTs and GO. In addition, the close contact between the CoS2 nanoparticles and carbon networks enabled by the Co-N chemical bond prevents the self-aggregation of the CoS2 nanoparticles. As a result, the CoS2/GO/CNTs flexible film delivered superior rate capability (213.5 mAh g−1 at 6 A g−1, better than most reported flexible anode) and long-term cycling stability. Moreover, the conversion reaction that occurred in the CoS2/GO/CNTs flexible film exhibited pseudocapacitive behavior. This study provides meaningful insights into the development of flexible electrodes with superior mechanical properties and electrochemical performance for energy storage.

Biomass Waste Utilization as Nanocomposite Anodes through Conductive Polymers Strengthened SiO2/C from Streblus asper Leaves for Sustainable Energy Storages.

Sustainable anode materials, including natural silica and biomass-derived carbon materials, are gaining increasing attention in emerging energy storage applications. In this research, we highlighted a silica/carbon (SiO2/C) derived from Streblus asper leaf wastes using a simple method. Dried Streblus asper leaves, which have plenty of biomass in Thailand, have a unique leaf texture due to their high SiO2 content. We can convert these worthless leaves into SiO2/C nanocomposites in one step, producing eco-materials with distinctive microstructures that influence electrochemical energy storage performance. Through nanostructured design, SiO2/C is thoroughly covered by a well-connected framework of conductive hybrid polymers based on the sodium alginate-polypyrrole (SA-PPy) network, exhibiting impressive morphology and performance. In addition, an excellent electrically conductive SA-PPy network binds to the SiO2/C particle surface through crosslinker bonding, creating a flexible porous space that effectively facilitates the SiO2 large volume expansion. At a current density of 0.3 C, this synthesized SA-PPy@Nano-SiO2/C anode provides a high specific capacity of 756 mAh g-1 over 350 cycles, accounting for 99.7% of the theoretical specific capacity. At the high current of 1 C (758 mA g-1), a superior sustained cycle life of over 500 cycles was evidenced, with over 93% capacity retention. The research also highlighted the potential for this approach to be scaled up for commercial production, which could have a significant impact on the sustainability of the lithium-ion battery industry. Overall, the development of green nanocomposites along with polymers having a distinctive structure is an exciting area of research that has the potential to address some of the key challenges associated with lithium-ion batteries, such as capacity degradation and safety concerns, while also promoting sustainability and reducing environmental impact.

Rational design of hierarchical porous reduced graphene oxide/9,10-phenanthraquinone/porous carbon nanocomposites for high-performance supercapacitors

The development of advanced electrode material is crucial for promoting the application of new high-performance green energy storage devices and remains a great challenge. Herein, by introducing porous carbon (PC) or carbon nanotubes (CNTs) to further modify the redox-active 9,10-phenanthrenequinone (PQ) molecule non-covalently functionalized reduced graphene oxide (RGO), we have designed and synthesized RGO/PQ/PCs (RPPs) and RGO/PQ/CNTs-10 (RPC-10) nanocomposites using a simple one-step solvothermal method. Benefiting from the optimization of the hierarchical porous nanostructures and each composition further strengthens their respective advantages in the novel synthesized nanocomposites (RPPs and RPC-10), the RPPs and RPC-10 electrodes demonstrated significantly superior electrochemical energy storage performance over the RGO and RGO/PQ (RP) electrodes, especially for the RPP-10 electrode with a high specific capacitance of 343.5 F g−1 at 0.5 A g−1 and good rate capability (69.23 %, 0.5 − 40 A g−1). Furthermore, both the symmetric supercapacitor assembled with the optimal RPP-10 electrode and the hybrid supercapacitor assembled with the RPP-10 negative electrode and the NCSRC-24 positive electrode previously reported show excellent energy densities and ultra-long cycling stabilities. This result demonstrates that the synthesized novel RPP-10 nanocomposite is a highly promising candidate for new light-weight, sustainable, high-flexible and high-performance energy storage devices.

Construction of rod-like micro/nano structure and its effects on the electrochemical energy storage performance of lithium-rich manganese-based cathode material

Construction of rod-like micro/nano structure and its effects on the electrochemical energy storage performance of lithium-rich manganese-based cathode material

Electrochemical charge storage performance of (Mn, Ni, Mo, Co, Fe)3O4 high entropy oxide nanoparticles produced via thermal plasma route

Highly complex high entropy metal oxides (HEOs) have several unique characteristics, such as more active sites and material stability that improve the electrochemical charge storage capacity. In this study, HEOs (Mn, Ni, Mo, Co, Fe)3O4 nanoparticles were synthesized using a thermal plasma route and its electrochemical energy storage performance was studied with two distinct electrolytes such as 1 M KOH and NaOH. The X-ray diffraction analysis revealed the phase pure spinel structured HEOs with crystalline size ranging from 13 to 29 nm. Scanning electron microscopy and electron dispersive X-ray spectroscopy results revealed the quasi-spherical morphology and uniform distribution of constitutional cations in the as-synthesized HEOs. The X-ray photoelectron spectroscopy results identified the oxidation states of cations in spinel HEOs. The charge/discharge studies of as-synthesized HEOs showed a specific capacitance of 215 F g-1 /26.9 mAh g-1 at a current density of 2 A g-1 in 1 M KOH electrolyte which is 156 % greater than 1 M NaOH electrolyte. Furthermore, a high capacitance retention of 91 % was achieved after completing 3000 cycles at 10 A g-1 current density which indicates that the HEOs have excellent charge/discharge reversibility. Electrochemical impedance spectroscopy revealed that the solution and charge transfer resistances of HEOs electrodes were 1.04 and 3.2 Ω, respectively. This novel synthesis strategy attempts to overcome the difficulties experienced by established methods for bulk manufacture of phase pure HEOs since thermal plasma method is a rapid and a single-step approach for the bulk production of nanomaterial.