A multidimensional rational design of nickel-iron sulfide and carbon nanotubes on diatomite via synergistic modulation strategy for supercapacitors

Alloying Confined Regulation of Nanoparticles in a Hierarchically Directed Porous Carbon for Zinc-Air Batteries

The rational design of non-noble metal-based electrocatalysts with efficient bifunctional catalytic activity is critical for the widespread application of zinc-air batteries (ZABs). In this study, an FeNi alloy encapsulated three-dimensional honeycomb-like network structure of carbon aerogels (FeNi/CAs) electrocatalyst was constructed using directional freeze-drying technology. The innovative architecture, combined with the synergistic effect between Fe and Ni, endows the FeNi/CAs catalyst with outstanding bifunctional catalytic activity compared with the introduction of a single metal in carbon aerogels. Specifically, the catalyst achieves a high half-wave potential (E1/2) of 0.90 V for the oxygen reduction reaction (ORR) and excellent stability with a negligible shift of E1/2 (9 mV) after 2000 cycles. Moreover, the FeNi/CAs catalyst exhibits a smaller potential difference (ΔE = 0.68 V) between the ORR and oxygen evolution reaction (OER), highlighting its superior bifunctional activity. Furthermore, the rechargeable ZABs with FeNi/CAs catalysts show remarkable power density (226 mW cm-2) and energy density (985 mWh kg-1), as well as over 1200 h of cycling stability. Additionally, the discharge rate performance of the assembled flexible all-solid-state battery based on this catalyst remains stable under different bending angles, suggesting its robustness and potential for use in wearable electronic devices. This work provides a compelling strategy for the construction of advanced electrocatalysts by leveraging hierarchical structural features and metal synergy, paving the way for high-performance and durable ZABs in next-generation energy storage applications.

Tailoring a hierarchical porous carbon electrode from carbon black via 3D diatomite morphology control for enhanced electrochemical performance

Carbon black, a nano-porous material usually derived from the pyrolysis of waste tyres possesses varied particle sizes and morphology making it a viable material for several engineering applications. However, the high tendency for CB to agglomerate remains a challenge. To address this, bio-templating has been employed to produce a nanostructured porous carbon electrode material for supercapacitor applications using diatomite as a template. Diatomite-synthesized activated carbon (DSAC) was fabricated through a three-step process involving acid treatment of diatomite, thermal activation of carbon black, and bio-template synthesis. The resulting material was thoroughly characterized using XRD, Raman spectroscopy, BET analysis, and SEM imaging. Its electrochemical properties were assessed through cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The DSAC material exhibited a high specific surface area of 266.867 m2 g-1, pore volume of 0.6606 cm3 g-1, and mean pore radius of 1.8943 nm. The electrochemical evaluation revealed that DSAC demonstrates excellent electrochemical performance, achieving a high specific capacitance of 630.18 F g-1 and retaining 94.29% capacitance after 5000 cycles at 1 A g-1. The DSAC electrode is eco-friendly and a promising candidate for supercapacitor applications.

Photothermal-Enhanced S-Scheme Heterojunction of Hollow Core-Shell FeNi2S4@ZnIn2S4 toward Photocatalytic Hydrogen Evolution

Herein, guided by the results of density functional theory prediction, the study rationally designs a hollow core-shell FeNi2S4@ZnIn2S4 (FNS@ZIS) Step-scheme (S-scheme) heterojunction for photocatalytic H2 evolution with photothermal-assisted. The hollow FNS spheres offered substrate for coating the ZIS nanosheets, which can inhibit ZIS nanosheets from agglomerating into pellet, enrich the active site, increase specific surfaces, and raise the light absorption. Notably, due to its excellent photothermal properties, FNS core generated heat unceasingly inside under visible-light irradiation and effectively prevent the heat loss of the reaction system, which increased the local temperature of photocatalysts and thus accelerated the charge migration. In addition, the S-scheme heterojunction construction via in situ growth has a tight interface, which can facilitate the separation and transfer of carriers and achieve high redox potential. Owning to the distinctive construction, the hollow core-shell FNS@ZIS S-scheme heterojunction show extraordinary stability and photocatalytic H2 evolution rate with 7.7 mmol h-1 g-1, which is ≈15.2-fold than pristine ZIS. Based on the double evidence of theoretical predictions and experimental confirmations, the photothermal effect and electron transfer mechanism of this innovative material are investigated in depth by the following infrared thermography technology and deep DFT calculations.

Designing transition metal-based porous architectures for supercapacitor electrodes: a review

Over the past decade, transition metal (TM)-based electrodes have shown intriguing physicochemical properties and widespread applications, especially in the field of supercapacitor energy storage owing to their diverse configurations, composition, porosity, and redox reactions. As one of the most intriguing research interests, the design of porous architectures in TM-based electrode materials has been demonstrated to facilitate ion/electron transport, modulate their electronic structure, diminish strain relaxation, and realize synergistic effects of multi-metals. Herein, the recent advances in porous TM-based electrodes are summarized, focusing on their typical synthesis strategies, including template-mediated assembly, thermal decomposition strategy, chemical deposition strategy, and host-guest hybridization strategy. Simultaneously, the corresponding conversion mechanism of each synthesis strategy are reviewed, and the merits and demerits of each strategy in building porous architectures are also discussed. Subsequently, TM-based electrode materials are categorized into TM oxides, TM hydroxides, TM sulfides, TM phosphides, TM carbides, and other TM species with a detailed review of their crystalline phase, electronic structure, and microstructure evolution to tune their electrochemical energy storage capacity. Finally, the challenges and prospects of porous TM-based electrode materials are presented to guide the future development in this field.

P-N heterojunction NiO/ZnO nanowire based electrode for asymmetric supercapacitor applications

Nickel-based oxides are selected for their inexpensive cost, well-defined redox activity, and flexibility in adjusting nanostructures via optimization of the synthesis process. This communique explores the field of energy storage for hydrothermally synthesized NiO/ZnO nanowires by analysing their capacitive behaviour. The p-type NiO was successfully built onto the well-ordered mesoporous n-type ZnO matrix, resulting in the formation of p-n heterojunction artefacts with porous nanowire architectures. NiO/ZnO nanowire-based electrodes exhibited much higher electrochemical characteristics than bare NiO nanowires. The heterojunction at the interface between the NiO and ZnO nanoparticles, their specific surface area, as well as their combined synergetic influence, are accountable for the high specific capacitance (Cs) of 1135 Fg-1at a scan rate of 5 mV s-1. NiO/ZnO nanowires show an 18% dip in initial capacitance even after 6000 cycles, indicating excellent capacitance retention and low resistance validated by electrochemical impedance spectroscopy. In addition, the specific capacitance, energy and power density of the solid state asymmetric capacitor that was manufactured by employing NiO/ZnO as the positive electrode and activated carbon as the negative electrode were found to be 87 Fg-1, 23 Whkg-1and 614 Wkg-1, respectively. The novel electrode based on NiO/ZnO demonstrates excellent electrochemical characteristics all of which point to its promising application in supercapacitor devices.

Spongelike Bimetallic Selenides Derived from Prussian Blue Analogue on Layered Ni(II)-Based MOF for High-Efficiency Supercapacitors

Recently, employing metal-organic frameworks (MOFs) as precursors to prepare various metal oxides, sulfides, and selenides has drawn enormous attention in the field of energy storage. In this paper, the nanosheets of an organophosphate-based Ni-MOF were successfully synthesized and employed as the template to prepare the Prussian blue analogue (PBA) nanoslices and nanoparticles on the nanosheet (PBA/Ni-MOF-NS-x h, x h stands for the reaction time.) by an in situ etching method. After selenization by the solvothermal method, the PBA nanoslices and nanoparticles were transformed into spongelike bimetallic selenides (labeled as PBA/Ni-MOF-NS-x h-Se) decorated with some nanoparticles. All of the characterization results including PXRD, SEM, TEM, EDS, XPS, and BET demonstrated the successful transformation. Impressively, the as-synthesized PBA/Ni-MOF-NS-12 h-Se exhibited a high specific capacitance of 1897.90 F g-1 at a current density of 1 A g-1 and a superior capacitance retention rate of 73.32% as the current density increased to 20 A g-1. In addition, the asymmetric supercapacitor device, PBA/Ni-MOF-NS-12 h-Se//AC, delivered a high energy density of 30.69 W h kg-1 at 0.85 kW kg-1 and extraordinary cycling stability with an 83.00% capacitance retention rate over 5000 cycles.

Constructing nickel sulfide @ nickel boride hybrid nanosheet arrays with crystalline/amorphous interfaces for supercapacitors

Designing a heterostructure with unique morphology and nanoarchitecture is regarded as an efficient strategy to achieve high-energy-density supercapacitors (SCs). Herein, a rational nickel sulfide @ nickel boride (Ni9S8@Ni2B) heterostructure is in situ synthesized on carbon cloth (CC) substrate via a simple electrodepositon strategy followed by a chemical reduction method. The three-dimensional hierarchically porous Ni9S8@Ni2B nanosheet arrays, consisting of crystalline Ni9S8 nanosheets and amorphous Ni2B nanosheets, can expose ample electroactive centers, shorten ion diffusion distance, and buffer volume changes during charging/discharging process. More importantly, the generation of crystalline/amorphous interfaces in the Ni9S8@Ni2B composite modulates its electrical structure and improves electrical conductivity. Owing to the synergy of Ni9S8 and Ni2B, the as-synthesized Ni9S8@Ni2B electrode acquires a specific capacity of 901.2C g-1 at 1 A g-1, a sound rate capability (68.3% at 20 A g-1), along with good cycling performance (79.7% capacity retention over 5000 cycles). Additionally, the assembled Ni9S8@Ni2B//porous carbon asymmetric supercapacitor (ASC) exhibits a cell voltage of 1.6 V and a maximum energy density of 59.7 Wh kg-1 at 805.2 W kg-1. These findings might offer a simple and innovative approach to fabricate advanced electrode materials for high-performance energy storage systems.

Characterization of Chitosan-Hybridized Diatomite as Potential Delivery Systems of Oxaliplatin and 5-Fluorouracil Drugs: Equilibrium and Release Kinetics

The current work involves the modification of diatomite's biosiliceous frustules employing chitosan polymer chains (CS/Di) to serve as low-cost, biocompatible, multifunctional, and enhanced pharmaceutical delivery systems for 5-fluorouracil (5-Fu) together with oxaliplatin (OXPL). The CS/Di carrier displayed strong loading characteristics, notably at saturation (249.17 mg/g (OXPL) and 267.6 mg/g (5-Fu)), demonstrating a substantial 5-Fu affinity. The loading of the two types of medications onto CS/Di was conducted based on the kinetic behaviors of the conventional pseudo-first-order theory (R2 > 0.90). However, while the loading of OXPL follows the isotherm assumptions of the classic Langmuir model (R2 = 0.99), the loading of 5-Fu displays Fruendlich isotherm properties. Therefore, the 5-Fu loading displayed physical, heterogeneous, and multilayer loading properties, whereas the loading of OXPL occurred in homogeneous and monolayer form. The densities of occupied active sites of CS/Di were 37.19 and 32.8 mg/g for the sequestrations of OXPL and 5-Fu, respectively. Furthermore, by means of multimolecular processes, each loading site of CS/Di can bind up to 8 molecules of OXPL and 9 molecules of 5-Fu in a vertical orientation. This observation explains the higher loading capacities of 5-Fu in comparison to OXPL. The loading energies, which exhibit values <40 kJ/mol, provide confirmation of the dominant and significant consequences of physical processes as the regulating mechanisms. The release patterns of OXPL and 5-Fu demonstrate prolonged features over a duration of up to 120 h. The release kinetic simulation and diffusion exponents which are more than 0.45 provide evidence of the release of OXP and 5-Fu via non-Fickian transportation characteristics and the erosion/diffusion mechanism. The CS/Di carrier exhibited a substantial enhancement in the cytotoxicity of OXPL and 5-Fu against HCT-116 carcinoma cell lines, resulting in a reduction in cell viability by 4.61 and 2.26% respectively.

A three-dimensional interconnected molybdenum disulfide/multi-walled carbon nanotubes cathode with enlarged interlayer spacing for aqueous zinc-ion storage

Layered molybdenum disulfide (MoS₂) shows tremendous prospect as cathode material for aqueous zinc-ion batteries (AZIBs) due to the two-dimensional zinc ions (Zn²⁺) diffusion channels and tunable interlayer spacing. However, it is subjected to sluggish insertion/extraction kinetics, inferior electronic conductivity and inadequate active capacities. Herein, a three-dimensional (3D) interconnected MoS₂/multi-walled carbon nanotubes (MWCNTs) framework is proposed to address these issues. Importantly, the MWCNTs cores offer interconnection routes for fast electrons and zinc ions transport, the expanded spacing of MoS₂ interlayer with 1.05 nm can facilitate rapid Zn²⁺ intercalation/extraction, and the confined MoS₂ layers in inner MWCNTs can mitigate the agglomeration and restacking of MoS₂ nanosheets. Benefitting from the confined structural configuration, sufficient active surface and 3D structural stability, the MoS₂/MWCNTs as AZIBs cathode delivers a large initial reversible capacity of 218.3 mAh/g and high coulombic efficiency of 78.2 % at 0.1 A/g. Additionally, the 3D interconnected cathode maintains nearly intact structure after a fierce galvanostatic charge/discharge process, resulting in large retained capacities of 126.3 mAh/g at 1 A/g after 650 cycles and 101.1 mAh/g at 3 A/g after 1000 cycles. This work offers a novel strategy for the structure design of two-dimensional materials to develop high-performance cathodes for AZIBs.

Optimization of bandgap reduction in 2-dimensional GO nanosheets and nanocomposites of GO/iron-oxide for electronic device applications

In this report we have developed different fabrication parameters to tailor the optical bandgap of graphene oxide (GO) nanosheets to make it operational candidate in electronic industry. Here we performed two ways to reduce the bandgap of GO nanosheets. First, we have optimized the oxidation level of GO by reducing amount of oxidizing agent (i.e. KMnO₄) to control the sp²/sp³ hybridization ratio for a series of GO nanosheets samples. We noticed the reduction in primary band edge 3.93-3.2 eV while secondary band edge 2.98-2.2 eV of GO nanosheets as the amount of KMnO₄ is decreased from 100 to 30%. Second, we have fabricated a series of 2-dimensional nanocomposites sample containing GO/Iron-oxide by using a novel synthesis process wet impregnation method. XRD analysis of synthesized nanocomposites confirmed the presence of both phases,[Formula: see text]-Fe₂O₃ and Fe₃O₄ of iron-oxide with prominent plane (001) of GO. Morphological investigation rules out all the possibilities of agglomerations of iron oxide nanoparticles and coagulation of GO nanosheets. Elemental mapping endorsed the homogeneous distribution of iron oxide nanoparticles throughout the GO nanosheets. Raman spectroscopy confirmed the fairly constant I_D/I_G ratio and FWHM of D and G peaks, thus proving the fact that the synthesis process of nanocomposites has no effect on the degree of oxidation of GO flakes. Red shift in G peak position of all the nanocomposites samples showed the electronic interaction among the constituents of the nanocomposite. Linear decrease in the intensity of PL (Photoluminescence) spectra with the increasing of Iron oxide nanoparticles points towards the increased interaction among the iron oxide nanoparticles and GO flakes. Optical absorption spectroscopy reveals the linear decrease in primary edge of bandgap from 2.8 to 0.99 eV while secondary edge decrease 3.93-2.2 eV as the loading of [Formula: see text]-Fe₂O₃ nanoparticles is increased from 0 to 5% in GO nanosheets. Among these nanocomposites samples 5%-iron-oxide/95%-GO nanosheet sample may be a good contestant for electronic devices.

Na superionic conductor-type compounds as protective layers for dendrites-free aqueous Zn-ion batteries

Aqueous rechargeable Zn-ion batteries (ARZIBs) have attracted much attention owing to their safety, high energy density and environmental friendliness. However, dendrite formation and corrosive reactions on Zn anode surface limit the development of ARZIBs. Here, Ga3+-doped NaV2(PO4)3 with Na superionic conductor (NASICON) structure [NVP-Ga(x), x = 0, 0.25, 0.5, 0.75] have been exploited as the high-efficiency artificial layer to stabilize Zn anode. The optimal NVP-Ga(0.5) layer can homogenize ion flux and promote uniform deposition of zinc, the dendrite growth and the parasitic reactions can be greatly inhibited. The symmetric cell based on this unique protection layer can stably operate over 1,300 h at 0.5 mA cm-2 with 0.5 mAh cm-2. Benefitting from the high-performance Zn metal anode, the full batteries paired with MnO2 cathode deliver a high discharge capacity of 106 mAh/g with the capacity retention rate of 85 % after 8,000 cycles. This work provides an advanced strategy to stabilize Zn anode for the industrialization of ARZIBs in the near future.

Core-Shell Structured SiO2@NiFe LDH Composite for Broadband Electromagnetic Wave Absorption

In this work, a novel core-shell structure material, NiFe layered double hydroxide (NiFe LDH) loaded on SiO2 microspheres (SiO2@NiFe LDH), was synthesized by a one-step hydrothermal method, and the spontaneous electrostatic self-assembly process. The morphology, structure, and microwave absorption properties of SiO2@NiFe LDH nanocomposites with different NiFe element ratios were systematically investigated. The results show that the sample of SiO2@NiFe LDH-3 nanocomposite has excellent microwave absorption properties. It exhibits broadband effective absorption bandwidth (RL < −10 dB) of 8.24 GHz (from 9.76 GHz to 18.0 GHz) and the reflection loss is −53.78 dB at the matched thickness of 6.95 mm. It is expected that this SiO2@NiFe-LDH core-shell structural material can be used as a promising non-precious, metal-based material microwave absorber to eliminate electromagnetic wave contamination.

Microwave Absorption of α-Fe2O3@diatomite Composites

A neoteric round sieve diatomite (De) decorated with sea-urchin-like alpha-type iron trioxide (α-Fe₂O₃) synthetics was prepared by the hydrothermal method and further calcination. The results of the electromagnetic (EM) parameters of α-Fe₂O₃-decorated De (α-Fe₂O₃@D) showed that the minimum reflection loss (RL_min) of α-Fe₂O₃@D could reach -54.2 dB at 11.52 GHz and the matched absorber thickness was 3 mm. The frequency bandwidth corresponding to the microwave RL value below -20 dB was up to 8.24 GHz (9.76-18 GHz). This indicates that α-Fe₂O₃@D composite can be a lightweight and stable material; because of the low density of De (1.9-2.3 g/cm³), the density of α-Fe₂O₃@D composite material is lower than that of α-Fe₂O₃ (5.18 g/cm³). We found that the combination of the magnetic loss of sea-urchin-like α-Fe₂O₃ and the dielectric loss of De has the most dominant role in electromagnetic wave absorption and loss. We focused on comparing the absorbing properties before and after the formation of sea-urchin-like α-Fe₂O₃ and explain in detail the effects of the structure and crystal shape of this novel composite on the absorbing properties.

Novel design of Sulfur-doped nickel cobalt layered double hydroxide and polypyrrole nanotube composites from zeolitic imidazolate Framework-67 as efficient active material of battery supercapacitor hybrids

Nickel and cobalt layered double hydroxide (NiCo-LDH) has large specific surface area and interlayer spacing, multiple redox states and high ion-exchange capability, but poor electrical conductivity, severe agglomerations and structural defect restrict energy storage ability of NiCo-LDH as active materiel of battery supercapacitor hybrids (BSH). In this study, it is the first time to design sulfur-doped NiCo-LDH and polypyrrole nanotubes composites (NiCo-LDH-S/PNTs) from zeolitic imidazolate framework-67 (ZIF-67) as the efficient active material of BSH using electrospinning and hydrothermal processes. Effects of sulfur doping amounts are investigated. The one-dimensional hollow polypyrrole decorated with NiCo-LDH-S sheets with high aspect ratio provides straight charge-transfer routes and abundant contacts with electrolyte. The highest specific capacitance (C_F) of 1936.3 F/g (specific capacity of 322.8 mAh/g) is achieved for the NiCo-LDH-S/PNTs with sulfur doping amount of 7% at 10 mV/s. The BSH comprising graphene LDH negative electrode and NiCo-LDH-S/PNTs positive electrode shows the maximum energy density of 16.28 Wh/kg at 650 W/kg. The C_F retention of 74% and Coulombic efficiency of 90% are also achieved after 8000 charge/discharge cycles.

Biomimetic Swallow Nest Structure: A Lightweight and High-Strength Thermal Insulation Material

A common method for reducing carbon emissions and the load-bearing pressure of buildings, and while also achieving improved energy conservation is to prepare porous magnesium-based lightweight composites to reduce waste and environmental hazards. However, due to internal stress, the pores of traditional lightweight composites crack easily and collapse, resulting in composites that are brittle with poor water resistance. These materials cannot achieve both low density and high strength, which limits their application in advanced functional materials. Thus, learned from nature, inspired by swallow's nest, a solution has been proposed, which is a simple and fast chemical arrangement and assembly method. Using bamboo scraps as the supporting framework and methylcellulose (MC) molecular chains as the templates, 5-phase crystals are grown and arranged on the MC. These crystals are arranged on the bamboo scraps by chemical means with MC acting as a bridge. At the same time, using the high viscosity and flexibility of the vinyl acetate/ethylene (VAE) copolymer emulsion and the formation of magnesium acetate chelate from VAE and hydration products, crystals and bamboo scraps can be assembled. Through these organic-inorganic copolymers, an intercalated and integrated biomimetic swallow nest structure is formed. The biomimetic swallow nest structure composites (BSNSC) imitated the formation process of a natural swallow nest. It is a lightweight material with a thick wall, low connectivity rate, and regular shape. Its density is 0.42 g/cm³, which is still in the density class of ultralight inorganic foam materials, and its compressive strength reaches 6.5 MPa, three times that of ordinary composites. The structure has a strength-to-weight ratio 3.5 times that of ordinary composites and a thermal conductivity much lower than of other thermal insulation materials. In the future, this type of lightweight composites with high strength, high heat insulation, and low density not only functions as a good energy-saving material for buildings but also a good thermal insulation material in the aerospace field.

Multi-step electrodeposited Ni-Co-P@LDH nanocomposites for high-performance interdigital asymmetric micro-supercapacitors

The development of high-performance electrode materials and the rational design of asymmetric structures are the two main keys to fabricating micro-supercapacitors (MSCs) with high energy density. Transition metal compounds, especially nickel-cobalt phosphides and hydroxides, are promising electrode materials with excellent pseudo-capacitance. However, they are rarely used in fabricating asymmetric MSCs (AMSCs) due to the limitations of the preparation method. In this work, we constructed hierarchical Ni-Co-P@LDH nanocomposites with outstanding mass specific capacitance (1980 F g^-1 at 1 A g^-1) via a multi-step electrodeposition method, which is employed with FeOOH to fabricate an interdigital AMSC device (Ni-Co-P@LDHs//PVA-KOH//FeOOH). The as-prepared device exhibits a high working voltage (1.4 V), a large specific capacitance (24.0 mF cm^-2 at 0.14 mA cm^-2), a high energy density (6.54 μW h cm^-2 at a power density of 100 μW cm^-2) and good cycling stability (86.5% of capacitance retention after 5000 cycles). This work may provide novel methods for the synthesis of high-performance nickel-cobalt composite materials and their potential applications in interdigital AMSC devices.

Electrochemical Performance of MnO2/Graphene Flower-like Microspheres Prepared by Thermally-Exfoliated Graphite

To enhance the electrochemical performance of MnO₂/graphene composite, herein, thermally-exfoliated graphite (TE-G) is adopted as a raw material, and a hydrothermal reaction is conducted to achieve the exfoliation of TE-G and the loading of MnO₂ nanosheets. Through optimizing the TE-G/KMnO₄ ratio in the redox reaction between carbon and KMnO₄, flower-like MnO₂/G microspheres (MnO₂/G-10) are obtained with 83.2% MnO₂ and 16.8% residual graphene. Meanwhile, corresponding MnO₂/rGO composites are prepared by using rGO as raw materials. Serving as a working electrode in a three-electrode system, MnO₂/G-10 composite displays a specific capacitance of 500 F g⁻¹ at 1 A g⁻¹, outstanding rate performance, and capacitance retention of 85.3% for 5,000 cycles. The performance is much better than that of optimized MnO₂/rGO composite. We ascribe this to the high carbon fraction in TE-G resulting in a high fraction of MnO₂ in composite, and the oxygen-containing groups in rGO reduce the resulting MnO₂ fraction in the composite. The superior electrochemical performance of MnO₂/G-10 is dependent on the hierarchical porous structure constructed by MnO₂ nanosheet arrays and the residual graphene layer in the composite. In addition, a supercapacitor assembled by TE-G negative electrode and MnO₂/G positive electrode also exhibits superior performance. In consideration of the low cost of raw materials, the MnO₂/G composite exhibits great application potential in the field of supercapacitors.

Carbon spheres decorated-graphene oxide framework as an excellent active material for redox flow battery and supercapacitors

Composite of dextrose-derived oxygen-rich carbon spheres and graphene oxide, synthesised using a cost-effective and easy hydrothermal process, was used as an active material in two of the trending and promising energy storage devices. The surface morphology and properties of the composite were studied using scanning electron microscope, X-ray diffractometer, energy dispersive X-ray analysis, elemental mapping and Raman spectra. To analyse the electrochemical behaviour of the material, several electrochemical techniques such as cyclic voltammetry (CV), chronopotentiometry, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation study were used. The reversibility of Fe²⁺/Fe³⁺ redox species and resistance offered by electrolyte towards the modified electrode were studied using CV, EIS and Tafel studies. Further evaluation of efficacy of the active material towards the iron redox flow battery (IRFB) of 132 cm² area was analysed by performing charge discharge studies at varied current densities. Substantial increase in the electrochemical performance of the IRFB with a coulombic efficiency (CE) 93% along with the good life cycle stability up to 25 cycles was observed. The composite was also used as a superior electrode material for supercapacitor application resulting in significant enhancement in the electrochemical performance with specific capacitance of 610 F g^-1 and CE of 83% with 93% retention up to 1600 cycles.

Nanostrucutured MnO2-TiN nanotube arrays for advanced supercapacitor electrode material

The capacitance of MnO2 supercapacitors (SCs) is not high as expected due to its low conductivity of MnO2. The synergistic effects of MnO2 with high theoretical specific capacitance and TiN with high theoretical conductivity can extremely enhance the electrochemical performance of the MnO2-TiN electrode material. In this work, we synthesized different nanostructured and crystalline-structured MnO2 modified TiN nanotube arrays electrode materials by hydrothermal method and explained the formation mechanism of different nanostructured and crystalline-structured MnO2. The influences of MnO2 nanostructures and crystalline-structures on the electrochemical performance has been contrasted and discussed. The specific capacitance of δ-MnO2 nanosheets-TiN nanotube arrays can reach 689.88 F g-1, the highest value among these samples TN-MO-SS, TN-MO-S, TN-MO-SR, TN-MO-RS, and TN-MO-R. The reason is explained based on MnO2 nanostructure and crystalline-structure and electron/ion transport properties. The specific capacitance retention rates are 97.2% and 82.4% of initial capacitance after 100 and 500 cycles, respectively, indicating an excellent charging-discharging cycle stability.

Facile synthesis of a 2D multilayer core–shell MnO2@LDH@MMT composite with a nanoflower shape for electromagnetic wave absorption

Manganese dioxide@NiFe layered double hydroxide@montmorillonite (MNFM) with a nanoflower-like two-dimensional layered core–shell construction has been successfully synthesized by a two-step hydrothermal method.

Atomic scaled modulation strategies and crystal phase transition of flower-like CoAl layered double hydroxide for supercapacitor

In the present work, cobalt aluminum layered double hydroxide and its derivatives were synthesized via hydrothermal method, alkali-etching method and phosphorization route to obtain different crystal phases. The structure, morphology...