Pillar-Supported 2D Layered MOFs with Abundant Active-Site Distributions for High-Performance Alkaline Supercapacitors

The development of two-dimensional (2D) layered metal-organic frameworks (MOFs) through precise molecular-level design and synthesis has emerged as a prominent research endeavor. However, the utilization of MOFs in their pristine form as electrodes for supercapacitors poses a significant challenge due to their limited tolerance in alkaline environments. To address these issues, we have developed Co- and Cu-based pillar-layered MOFs by regulating the structure of their inner layers through introducing an alkaline N-containing "pillar" to enhance the performance of alkaline supercapacitor electrodes. From the microstructure study and theoretical calculation, the high-density redox centers and efficient chemical bonding modes of Co-MOF determine a unique electron conduction pathway, resulting in excellent energy storage performance. This study underscores the significance of chemical bonding modes and active-site distribution in enhancing the energy storage capabilities of pillar-layered MOFs in alkaline environments, presenting a promising approach for the development of high-performance MOF-based materials for supercapacitor applications.

Screening Transition-Metal-Incorporated β-AgVO3 for Augmented Oxygen Reduction Activity

Exploring cost-effective alternatives to Pt-based catalysts for the oxygen reduction reaction (ORR) in fuel cells is crucial for their large-scale deployment in green energy applications. Silver vanadate (AgVO3) is a well-studied material for photocatalytic applications. Here, we investigate the electrocatalytic ORR activity of the thermodynamically stable β phase of AgVO3 through computational modeling based on DFT. It is found that β-AgVO3 exhibits weak catalytic activity for the ORR, with vanadium being the preferable active site. Incorporating single atoms of transition metals at surface-level vacancies in β-AgVO3 significantly modifies the ORR activity. We study the scaling of free energy changes for the ORR intermediates *OOH, *OH, and *O for various transition metals incorporated, which leads to an optimal overpotential for the system. The optimal overpotential thus obtained is remarkably lower than that of pristine β-AgVO3. For the transition metal atoms we consider here, Co-incorporated β-AgVO3 exhibits the best ORR catalytic activity due to its optimal binding of ORR species to the vanadium site. It is also observed that some of the transition metals considered like Re, Rh, Os, or Mn show weak activity, either due to strong or weak binding. Analysis of the electronic structure of the adsorbate-catalyst interface shows a strong correlation between optimal activity and evolution of midgap states in β-AgVO3, due to transition metal incorporation. Our study concludes that the ORR activity of a stable mixed transition metal oxide like β-AgVO3 can be enhanced with a minimal loading of transition metals, which could help in developing a novel series of ORR catalysts.

Hydrothermal Carbonization of Biomass for Electrochemical Energy Storage: Parameters, Mechanisms, Electrochemical Performance, and the Incorporation of Transition Metal Dichalcogenide Nanoparticles

Given the pressing climate and sustainability challenges, shifting industrial processes towards environmentally friendly practices is imperative. Among various strategies, the generation of green, flexible materials combined with efficient reutilization of biomass stands out. This review provides a comprehensive analysis of the hydrothermal carbonization (HTC) process as a sustainable approach for developing carbonaceous materials from biomass. Key parameters influencing hydrochar preparation are examined, along with the mechanisms governing hydrochar formation and pore development. Then, this review explores the application of hydrochars in supercapacitors, offering a novel comparative analysis of the electrochemical performance of various biomass-based electrodes, considering parameters such as capacitance, stability, and textural properties. Biomass-based hydrochars emerge as a promising alternative to traditional carbonaceous materials, with potential for further enhancement through the incorporation of extrinsic nanoparticles like graphene, carbon nanotubes, nanodiamonds and metal oxides. Of particular interest is the relatively unexplored use of transition metal dichalcogenides (TMDCs), with preliminary findings demonstrating highly competitive capacitances of up to 360 F/g when combined with hydrochars. This exceptional electrochemical performance, coupled with unique material properties, positions these biomass-based hydrochars interesting candidates to advance the energy industry towards a greener and more sustainable future.

Regulating the electronic properties, quantum capacitance and photocatalytic activity of Sc2CO2 based on Y doping and strain

The doping of transition metals can effectively modulate the electronic structures and enhance the photocatalytic activity of MXenes. The electronic and photocatalytic properties, as well as the quantum capacitance of Sc2CO2-Y under biaxial strain, were studied by density functional theory. Sc2CO2-Y is a direct semiconductor and keeps its semiconductor character under strain. Sc2CO2-Y under tensile strain has higher photocatalytic activity than under compressive strain. In particular, Sc2CO2-Y at 2% strain has the slowest recombination rate of electrons and holes because of the largest . Sc2CO2-Y under strain is a potential cathode material. Its large potential keeps the character of cathode materials for Sc2CO2-Y under strain. Sc2CO2-Y under tensile strain has better conductivity, especially under 5% strain, due to having the largest Re (ε0). Sc2CO2-Y under strain can perform the HER, but fails to perform the OER at pH = 0, and tensile strain increases the reduction capacity of Sc2CO2-Y. Under strains from -2% to 2%, Sc2CO2-Y can perform the OER in an alkaline environment. Sc2CO2-Y is a good CO2 photocatalyst in acidic environments; the increase of pH value weakens the N2 reducing capacity of Sc2CO2-Y under strain. Its work function, charge transfer and optical properties are also explored.

Synthesis, Modulation, and Application of Two-Dimensional TMD Heterostructures

Two-dimensional (2D) transition metal dichalcogenide (TMD) heterostructures have attracted a lot of attention due to their rich material diversity and stack geometry, precise controllability of structure and properties, and potential practical applications. These heterostructures not only overcome the inherent limitations of individual materials but also enable the realization of new properties through appropriate combinations, establishing a platform to explore new physical and chemical properties at micro-nano-pico scales. In this review, we systematically summarize the latest research progress in the synthesis, modulation, and application of 2D TMD heterostructures. We first introduce the latest techniques for fabricating 2D TMD heterostructures, examining the rationale, mechanisms, advantages, and disadvantages of each strategy. Furthermore, we emphasize the importance of characteristic modulation in 2D TMD heterostructures and discuss some approaches to achieve novel functionalities. Then, we summarize the representative applications of 2D TMD heterostructures. Finally, we highlight the challenges and future perspectives in the synthesis and device fabrication of 2D TMD heterostructures and provide some feasible solutions.

Nickel-Copper Bimetallic Oxide Nanoparticles Prepared by Simple Coprecipitation Method as High Performance Electrode Materials for Asymmetric Supercapacitors

Supercapacitors with transition bimetallic oxides as pseudocapacitive materials have been of wide concern for their excellent energy storage performance. In this work, a simple coprecipitation method was used to synthesize the precursor, followed by calcination to prepare Ni-Cu bimetallic oxide materials. The structure, morphology and properties of the materials prepared by different precipitating agents and different calcination temperatures of NCO-H2C2O4 precursor were investigated. The optimum precipitant was determined to be H2C2O4, and Ni-Cu nanoparticles with regular lamellar microstructure were obtained at the calcination temperature of 400 °C. The nanostructure and morphology provide a large active channel for the rapid diffusion of electrolyte ions, and the specific capacitance of NCO-H2C2O4-400 electrode material can reach 740.31 F/g Cs at 1 A/g. The investigation of charge storage mechanism shows that the contribution rate of capacitance and diffusion control is about 37.9% and 67.2%, respectively. The electrochemical test results of the asymmetric supercapacitors (ASC) constructed with NCO-H2C2O4-400 and activated carbon show that the specific capacitance, energy density, and power density of the capacitor are 52.66 F/g, 16.45 Wh/kg, and 759.51 W/kg, respectively. Even after 5000 charge/discharge cycles at 5 A/g, it can still keep 90.57% of its initial capacity. This work not only provides competitive electrode materials for energy storage devices but also provides a feasible strategy for producing complex transition metal oxide materials with high capacitance performance.

Highly Nanoporous Nickel Foam as Current Collectors in 3D All-Solid-State Microsupercapacitors

This study reports a streamlined method for producing a highly nanoporous current collector with a substantial specific surface area, serving as an electrode for microsupercapacitors (MSCs). Initially, commercial Ni foams are patterned into an interdigitated structure by laser cutting. Subsequently, the Ni foams are infused with NiO nanopowders through dip coating, sintering, and reduction in an H2 atmosphere, followed by the growth of MnO2 through a redox reaction. The incorporation of NiO within this three-dimensional Ni current collector results in notable porosity within the range of approximately 200-600 nm. Such a 3D, highly nanoporous electrode dramatically increases the specific surface area by 30 times and substantially boosts the amount of active material deposition, surpassing those of commercially available Ni foams. Performance evaluations of this highly nanoporous electrode in a 1 M KOH solution demonstrate an areal capacity of 19.3 F/cm2, retaining more than 95% capacitance at 5 mA/cm2, and exhibiting an energy density of 671 μW h/cm2, 25 times greater than commercial Ni foams. Moreover, in the realm of solid-state applications for MSCs, the remarkably high porous electrode achieves a commendable areal capacity of 7.22 F/cm2 and an energy density of 263.9 μW h/cm2, rendering it exceptionally suitable for use in MSC applications.

Molten Salt Derived MXenes: Synthesis and Applications

About one decade after the first report on MXenes, these 2D early transition metal carbides or nitrides have become among the best-performing materials in electrode applications related to electrical energy storage devices and power-to-fuels conversion. MXenes are obtained by a top-down approach starting from the appropriate 3D MAX phase that undergoes etching of the A-site metal. Initial etching procedures are based on the use of concentrated HF or the in situ generation of this highly corrosive and poisonous reagent. Etching of the MAX phase is one of the major hurdles limiting the progress of the field. The present review summarizes an alternative, universal, and easily scalable etching procedure based on treating the MAX precursor with a Lewis acid molten salt. The review starts with presenting the current state of the art of the molten salt etching procedure to obtain or modify MXene, followed by a summary of the applications of these MXene samples. The aim of the review is to show the versatility and advantages of molten salt etching in terms of general applicability, control of the surface terminal groups, and uniform deposition of metal nanoparticles, among other features of the procedure.

2D-on-2D Al-Doped NiCo LDH Nanosheet Arrays for Fabricating High-Energy-Density, Wide Voltage Window, and Ultralong-Lifespan Supercapacitors

Battery-type electrode materials with high capacity, wide potential windows, and good cyclic stability are crucial to breaking through energy storage limitations and achieving high energy density. Herein, a novel 2D-on-2D Al-doped NiCo layered double hydroxide (NiCoAlx LDH) nanosheet arrays with high-mass-loading are grown on a carbon cloth (CC) substrate via a two-step hydro/solvothermal deposition strategy, and the effect of Al doping is employed to modify the deposition behavior, hierarchical morphology, phase stability, and multi-metallic synergistic effect. The optimized NiCoAl0.1 LDH electrode exhibits capacities of 5.43, 6.52, and 7.25 C cm-2 (9.87, 10.88, and 11.15 F cm-2) under 0-0.55, 0-0.60, and 0-0.65 V potential windows, respectively, illustrating clearly the importance of the wide potential window. The differentiated deposition strategy reduces the leaching level of Al3+ cations in alkaline solutions, ensuring excellent cyclic performance (108% capacity retention after 40 000 cycles). The as-assembled NiCoAl0.1 LDH//activated carbon cloth (ACC) hybrid supercapacitor delivers 3.11 C cm-2 at 0-2.0 V, a large energy density of 0.84 mWh cm-2 at a power density of 10.00 mW cm-2, and excellent cyclic stability with ≈135% capacity retention after 150 000 cycles.

Conducting Polymer-Based Gel Materials: Synthesis, Morphology, Thermal Properties, and Applications in Supercapacitors

Despite the numerous ongoing research studies in the area of conducting polymer-based electrode materials for supercapacitors, the implementation has been inadequate for commercialization. Further understanding is required for the design and synthesis of suitable materials like conducting polymer-based gels as electrode materials for supercapacitor applications. Among the polymers, conductive polymer gels (CPGs) have generated great curiosity for their use as supercapacitors, owing to their attractive qualities like integrated 3D porous nanostructures, softness features, very good conductivity, greater pseudo capacitance, and environmental friendliness. In this review, we describe the current progress on the synthesis of CPGs for supercapacitor applications along with their morphological behaviors and thermal properties. We clearly explain the synthesis approaches and related phenomena, including electrochemical approaches for supercapacitors, especially their potential applications as supercapacitors based on these materials. Focus is also given to the recent advances of CPG-based electrodes for supercapacitors, and the electrochemical performances of CP-based promising composites with CNT, graphene oxides, and metal oxides is discussed. This review may provide an extensive reference for forthcoming insights into CPG-based supercapacitors for large-scale applications.

Application progress of nanomaterials in the treatment of prostate cancer

Prostate cancer is one of the most common malignant tumors in men, which seriously threatens the survival and quality of life of patients. At present, there are serious limitations in the treatment of prostate cancer, such as drug tolerance, drug resistance and easy recurrence. Sonodynamic therapy and chemodynamic therapy are two emerging tumor treatment methods, which activate specific drugs or sonosensitizers through sound waves or chemicals to produce reactive oxygen species and kill tumor cells. Nanomaterials are a kind of nanoscale materials with many excellent physical properties such as high targeting, drug release regulation and therapeutic monitoring. Sonodynamic therapy and chemodynamic therapy combined with the application of nanomaterials can improve the therapeutic effect of prostate cancer, reduce side effects and enhance tumor immune response. This article reviews the application progress of nanomaterials in the treatment of prostate cancer, especially the mechanism, advantages and challenges of nanomaterials in sonodynamic therapy and chemodynamic therapy, which provides new ideas and prospects for research in this field.

Conductive Polymer-Based Electrodes and Supercapacitors: Materials, Electrolytes, and Characterizations

New materials and the interactions between them are the basis of novel energy storage devices such as supercapacitors and batteries. In recent years, because of the increasing demand for electricity as an energy source, the development of new energy storage materials is among the most actively studied topics. Conductive polymers (CPs), because of their intrinsic electrochemical activity and electrical conductivity, have also been intensively explored. While most of the high capacitance reported in the literature comes from hybrid materials, for example, conductive polymers composed of metal oxides and carbon materials, such as graphene and carbon nanotubes, new chemistry and the 3D structure of conductive polymers remain critical. This comprehensive review focuses on the basic properties of three popular conductive polymers and their composites with carbon materials and metal oxides that have been actively explored as energy storage materials, i.e., polypyrrole (PPy), polyaniline (PANi), and polythiophene (PTh), and various types of electrolytes, including aqueous, organic, quasi-solid, and self-healing electrolytes. Important experimental parameters affecting material property and morphology are also discussed. Electrochemical and analytical techniques frequently employed in material and supercapacitor research are presented. In particular, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are discussed in detail, including how to extract data from spectra to calculate key parameters. Pros and cons of CP-based supercapacitors are discussed together with their potential applications.

A Highly Robust and Conducting Ultramicroporous 3D Fe(II)-Based Metal-Organic Framework for Efficient Energy Storage

Exploitation of metal-organic framework (MOF) materials as active electrodes for energy storage or conversion is reasonably challenging owing to their poor robustness against various acidic/basic conditions and conventionally low electric conductivity. Keeping this in perspective, herein, a 3D ultramicroporous triazolate Fe-MOF (abbreviated as Fe-MET) is judiciously employed using cheap and commercially available starting materials. Fe-MET possesses ultra-stability against various chemical environments (pH-1 to pH-14 with varied organic solvents) and is highly electrically conductive (σ = 0.19 S m-1) in one fell swoop. By taking advantage of the properties mentioned above, Fe-MET electrodes give prominence to electrochemical capacitor (EC) performance by delivering an astounding gravimetric (304 F g-1) and areal (181 mF cm-2) capacitance at 0.5 A g-1 current density with exceptionally high cycling stability. Implementation of Fe-MET as an exclusive (by not using any conductive additives) EC electrode in solid-state energy storage devices outperforms most of the reported MOF-based EC materials and even surpasses certain porous carbon and graphene materials, showcasing superior capabilities and great promise compared to various other alternatives as energy storage materials.

Recent Development on Transition Metal Oxides-Based Core-Shell Structures for Boosted Energy Density Supercapacitors

In recent years, nanomaterials exploration and synthesis have played a crucial role in advancing energy storage research, particularly in supercapacitor development. Researchers have diversified materials, including metal oxides, chalcogenides, and composites, as well as carbon materials, to enhance energy and power density. Balancing energy density with electrochemical stability remains challenging, driving intensified efforts in advancing electrode materials. This review focuses on recent progress in designing and synthesizing core-shell materials tailored for supercapacitors. The core-shell architecture offers advantages such as increased surface area, redox active sites, electrical conductivity, ion diffusion kinetics, specific capacitance, and cyclability. The review explores the impact of core and shell materials, specifically transition metal oxides (TMOs), on supercapacitor electrochemical behavior. Metal oxide choices, such as cobalt oxide as a preferred core and manganese oxide as a shell, are discussed. The review also highlights characterization techniques for assessing structural, morphological, and electrochemical properties of core-shell materials. Overall, it provides a comprehensive overview of ongoing TMOs-based core-shell material research for supercapacitors, showcasing their potential to enhance energy storage for applications ranging from gadgets to electric vehicles. The review outlines existing challenges and future opportunities in evolving TMOs-based core-shell materials for supercapacitor advancements, holding promise for high-efficiency energy storage devices.

Powering the Future by Iron Sulfide Type Material (FexSy) Based Electrochemical Materials for Water Splitting and Energy Storage Applications: A Review

Water electrolysis is among the recent alternatives for generating clean fuels (hydrogen). It is an efficient way to produce pure hydrogen at a rapid pace with no unwanted by-products. Effective and cheap water-splitting electrocatalysts with enhanced activity, specificity, and stability are currently widely studied. In this regard, noble metal-free transition metal-based catalysts are of high interest. Iron sulfide (FeS) is one of the essential electrocatalysts for water splitting because of its unique structural and electrochemical features. This article discusses the significance of FeS and its nanocomposites as efficient electrocatalysts for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and overall water splitting. FeS and its nanocomposites have been studied also for energy storage in the form of electrode materials in supercapacitors and lithium- (LIBs) and sodium-ion batteries (SIBs). The structural and electrochemical characteristics of FeS and its nanocomposites, as well as the synthesis processes, are discussed in this work. This discussion correlates these features with the requirements for electrocatalysts in overall water splitting and its associated reactions. As a result, this study provides a road map for researchers seeking economically viable, environmentally friendly, and efficient electrochemical materials in the fields of green energy production and storage.

Emerging Vanadium-Doped Cobalt Chloride Carbonate Hydroxide for Flexible Electrochromic Micro-Supercapacitor: Charged-State Prediction from RGB Input by ANN Model

Multifunctional devices integrated with electrochromic and supercapacitance properties are fascinating because of their extensive usage in modern electronic applications. In this work, vanadium-doped cobalt chloride carbonate hydroxide hydrate nanostructures (V-C3H NSs) are successfully synthesized and show unique electrochromic and supercapacitor properties. The V-C3H NSs material exhibits a high specific capacitance of 1219.9 F g-1 at 1 mV s-1 with a capacitance retention of 100% over 30 000 CV cycles. The electrochromic performance of the V-C3H NSs material is confirmed through in situ spectroelectrochemical measurements, where the switching time, coloration efficiency (CE), and optical modulation (∆T) are found to be 15.7 and 18.8 s, 65.85 cm2 C-1 and 69%, respectively. A coupled multilayer artificial neural network (ANN) model is framed to predict potential and current from red (R), green (G), and blue (B) color values. The optimized V-C3H NSs are used as the active materials in the fabrication of flexible/wearable electrochromic micro-supercapacitor devices (FEMSDs) through a cost-effective mask-assisted vacuum filtration method. The fabricated FEMSD exhibits an areal capacitance of 47.15 mF cm-2 at 1 mV s-1 and offers a maximum areal energy and power density of 104.78 Wh cm-2 and 0.04 mW cm-2, respectively. This material's interesting energy storage and electrochromic properties are promising in multifunctional electrochromic energy storage applications.

MOF-Derived Zn/N-Doped Porous Carbon Film on a Carbon Nanotube for High-Performance Supercapacitors

Designing high-performance binder-free electrochemical electrodes is crucially important toward supercapacitors. In this paper, a Zn/N-doped porous carbon film coating on flexible carbon nanotubes (ZIF-8@CT-800) derived from the epitaxial Zn-MOF film growth on cotton textile was successfully fabricated via a combination of the liquid-phase epitaxial (LPE) method and calcination treatments. The ZIF-8@CT-800 serves directly as a self-supported electrode for supercapacitors and exhibits a high areal capacitance of 930 mF·cm-2 at a current density of 1 mA·cm-2 and a good recyclability of 86% after 2000 cycles. The excellent supercapacitor property is ascribed to the unique structural design of ZIF-8@CT-800, which provides appropriate channels for enhanced electronic and ionic transport as well as increased surface area for accessing more electrolyte ions. This work will provide significant guidance for designing MOF-derived porous carbon to construct flexible binder-free electrode materials with high electrochemical performance.

Modeling of Nanomaterials for Supercapacitors: Beyond Carbon Electrodes

Capacitive storage devices allow for fast charge and discharge cycles, making them the perfect complements to batteries for high power applications. Many materials display interesting capacitive properties when they are put in contact with ionic solutions despite their very different structures and (surface) reactivity. Among them, nanocarbons are the most important for practical applications, but many nanomaterials have recently emerged, such as conductive metal-organic frameworks, 2D materials, and a wide variety of metal oxides. These heterogeneous and complex electrode materials are difficult to model with conventional approaches. However, the development of computational methods, the incorporation of machine learning techniques, and the increasing power in high performance computing now allow us to tackle these types of systems. In this Review, we summarize the current efforts in this direction. We show that depending on the nature of the materials and of the charging mechanisms, different methods, or combinations of them, can provide desirable atomic-scale insight on the interactions at play. We mainly focus on two important aspects: (i) the study of ion adsorption in complex nanoporous materials, which require the extension of constant potential molecular dynamics to multicomponent systems, and (ii) the characterization of Faradaic processes in pseudocapacitors, that involves the use of electronic structure-based methods. We also discuss how recently developed simulation methods will allow bridges to be made between double-layer capacitors and pseudocapacitors for future high power electricity storage devices.

Molybdenum Sulfide Nanoflowers as Electrodes for Efficient and Scalable Lithium-Ion Capacitors

Hybrid supercapacitors (HSCs) bridge the unique advantages of batteries and capacitors and are considered promising energy storage devices for hybrid vehicles and other electronic gadgets. Lithium-ion capacitors (LICs) have attained particular interest due to their higher energy and power density than traditional supercapacitor devices. The limited voltage window and the deterioration of anode materials upsurged the demand for efficient and stable electrode materials. Two-dimensional (2D) molybdenum sulfide (MoS2) is a promising candidate for developing efficient and durable LICs due to its wide lithiation potential and unique layer structure, enhancing charge storage efficiency. Modifying the extrinsic features, such as the dimensions and shape at the nanoscale, serves as a potential path to overcome the sluggish kinetics observed in the LICs. Herein, the MoS2 nanoflowers have been synthesized through a hydrothermal route. The developed LIC exhibited a specific capacitance of 202.4 F g-1 at 0.25 A g-1 and capacitance retention of >90 % over 5,000 cycles. Using an ether electrolyte improved the voltage window (2.0 V) and enhanced the stability performance. The ex-situ material characterization after the stability test reveals that the storage mechanism in MoS2-LICs is not diffusion-controlled. Instead, the fast surface redox reactions, especially intercalation/deintercalation of ions, are more prominent for charge storage.

Iodine Adsorption in Nanoporous Carbon to Fabricate Assimilated Battery Electrodes for Durable Hybrid Supercapacitors

A hybrid supercapacitor is designed by coupling a battery electrode with a capacitive electrode in a single device/cell to enhance energy density. In iodine-based hybrid supercapacitors, the nanoporous carbon serves as the electrode material; however, the cathode or positive electrode is charged with iodine via electrodeposition from a redox aqueous electrolyte, while a negative electrode stores charges at the electric double-layer. In this work, iodine is loaded via physical adsorption into the porosity of a carbon electrode, keeping the aqueous electrolyte free from iodide redox moieties. By this way, the risk of polyiodide (I3- and I5-) generation at the positive electrode leading to a shuttling-related performance loss of the hybrid supercapacitor is prevented. Chemical interactions of iodine with the carbon surface and within the pores have been investigated with Raman spectroscopy, thermogravimetry and electron microscopy. Electrochemical methods have been used to test individual electrodes and hybrid supercapacitors in aqueous NaNO3 and aqueous LiTFSI at 5 mol/L concentration for performance parameters such as energy efficiency, capacitance, self-discharge and cyclability. The hybrid supercapacitor in aqueous LiTFSI exhibits stable capacitance and energy efficiency during long-term aging tests at 1.5 V. Carbon nanoarchitecturing with iodine as shown in the present work offers an economical approach to enhance the performance of hybrid supercapacitors.

Unveiling the Role of Electrografted Carbon-Based Electrodes for Vanadium Redox Flow Batteries

Carbon-based electrodes are used in flow batteries to provide active centers for vanadium redox reactions. However, strong controversy exists about the exact origin of these centers. This study systematically explores the influence of structural and functional groups on the vanadium redox reactions at carbon surfaces. Pyridine, phenol and butyl containing groups are attached to carbon felt electrodes. To establish a unique comparison between the model and real-world behavior, both non-activated and commercially used thermally activated felts serve as a substrate. Results reveal enhanced half-cell performance in non-activated felt with introduced hydrophilic functionalities. However, this cannot be transferred to the thermally activated felt. Beyond a decrease in electrochemical activity, a reduced long-term stability can be observed. This work indicates that thermal treatment generates active sites that surpass the effect of functional groups and are even impeded by their introduction.

Differential capacitance of curved electrodes: role of hydration interactions and charge regulation

The functioning of supercapacitors relies on establishing electrostatic double-layer capacitance across a larger surface area, offering numerous advantages over conventional batteries, such as an extended lifespan and elevated safety standards. The differential capacitance is a fundamental property within the electrical double layer, playing a pivotal role in the advancement of electrical double-layer supercapacitors. In addition to electrostatic interactions, multiple theoretical and experimental studies have indicated that the differential capacitance is influenced by factors such as the physical structure of the electrode, solvent-mediated hydration interactions, and the specific type of electrolyte utilized. In this work, we incorporate hydration interactions into the Poisson-Boltzmann theory to explore curved electrodes whose surfaces can be covered by either acidic or basic groups. We examine how the electrostatic interaction, charge regulation, hydration effects, and the finite size of ions collectively modify the differential capacitance. Furthermore, we explore different scenarios of electrode curvature and how it may be used to achieve larger capacitance depending on the electrolyte type and pH.

Advanced Insights on MXenes: Categories, Properties, Synthesis, and Applications in Alkali Metal Ion Batteries

The development and optimization of promising anode material for next-generation alkali metal ion batteries are significant for clean energy evolution. 2D MXenes have drawn extensive attention in electrochemical energy storage applications, due to their multiple advantages including excellent conductivity, robust mechanical properties, hydrophilicity of its functional terminations, and outstanding electrochemical storage capability. In this review, the categories, properties, and synthesis methods of MXenes are first outlined. Furthermore, the latest research and progress of MXenes and their composites in alkali metal ion storage are also summarized comprehensively. A special emphasis is placed on MXenes and their hybrids, ranging from material design and fabrication to fundamental understanding of the alkali ion storage mechanisms to battery performance optimization strategies. Lastly, the challenges and personal perspectives of the future research of MXenes and their composites for energy storage are presented.

Cellulose-based aerogel derived N, B-co-doped porous biochar for high-performance CO2 capture and supercapacitor

The remarkable characteristics of porous biochar have generated significant interest in various fields, such as CO2 capture and supercapacitors. The modification of aerogel-derived porous biochar through activation and heteroatomic doping can effectively enhance CO2 adsorption and improve supercapacitor performance. In this study, a novel N, B-co-doped porous biochar (NBCPB) was synthesized by carbonating and activating the N, B dual-doped cellulose aerogel. N and B atoms were doped in-situ using a modified alkali-urea method. The potassium citrate was served as both an activator and a salt template to facilitate the formation of a well-developed nanostructure. The optimized NBCPB-650-1 (where 650 corresponded to activation temperature and 1 represented mass ratio of potassium citrate activator to carbonized NBCPB-400 precursor) displayed the largest micropore volume of 0.40 cm3·g-1 and a high specific surface area of 891 m2·g-1, which contributed to an excellent CO2 adsorption capacity of 4.19 mmol·g-1 at 100 kPa and 25 °C, a high CO2/N2 selectivity, and exceptional reusability (retained >97.5 % after 10 adsorption-desorption cycles). Additionally, the NBCPB-650-1 electrode also delivered a high capacitance of 220.9 F·g-1 at 1 A·g-1. Notably, the symmetrical NBCPB-650-1 supercapacitor exhibited a high energy density of 9 Wh·kg-1 at the power density of 100 W·kg-1. This study not only presents the potential application of NBCPB-650-1 material in CO2 capture and electrochemical energy storage, but also offers a new insight into easy-to-scale production of heteroatomic-modified porous biochar.

Controlling the graphite-like microcrystalline structure of lignin-based ultrafine carbon fibers via the design of condensed structures

Obtaining lignin-based graphite-like microcrystallites at a relatively low carbonization temperature is still very challenging. In this work, we report a new method based on condensed structures, for regulating graphite-like microcrystalline structures via the incorporation of 4,4'-diphenylmethane diisocyanate (MDI) into the main structure of lignin. The effects of MDI on the thermal properties of lignin and the graphite-like microcrystalline structure of lignin-based ultrafine carbon fibers were extensively studied and investigated. The incorporation of MDI decreased the thermal stability of lignin, increased the carbon yield and enhanced the formation of graphite-like microcrystallites, which are beneficial for reducing energy consumption during the preparation of lignin-based carbon fibers. The modified lignin-based ultrafine carbon fibers (M-LCFs) demonstrated satisfactory electrochemical performance, including high specific capacitance, low charge transfer resistance, and good cycle performance. The M-LCFs-3/2 electrode had a specific capacitance of 241.3 F g-1 at a current density of 0.5 A g-1, and a residual ratio of 90.2 % after 2000 charge and discharge cycles. This study provides a new approach to control the graphite-like microcrystalline structure and electrochemical performance while also optimizing the temperature.

A Comprehensive Review on Strategies for Enhancing the Performance of Polyanionic-Based Sodium-Ion Battery Cathodes

The significant consumption of fossil fuels and the increasing pollution have spurred the development of energy-storage devices like batteries. Due to their high cost and limited resources, widely used lithium-ion batteries have become unsuitable for large-scale energy production. Sodium is considered to be one of the most promising substitutes for lithium due to its wide availability and similar physiochemical properties. Designing a suitable cathode material for sodium-ion batteries is essential, as the overall electrochemical performance and the cost of battery depend on the cathode material. Among different types of cathode materials, polyanionic material has emerged as a great option due to its higher redox potential, stable crystal structure, and open three-dimensional framework. However, the poor electronic and ionic conductivity limits their applicability. This review briefly discusses the strategies to deal with the challenges of transition-metal oxides and Prussian blue analogue, recent developments in polyanionic compounds, and strategies to improve electrochemical performance of polyanionic material by nanostructuring, surface coating, morphology control, and heteroatom doping, which is expected to accelerate the future design of sodium-ion battery cathodes.

One-Step Cooperative Growth of High Reaction Kinetics Composite Homogeneous Core-Shell Heterostructure

Reaction kinetics can be improved by the enhanced electrical contact between different components growing symbiotically. But so far, due to the necessity for material synthesis conditions match, the component structures of cooperative growth are similar, and the materials are of the same type. The collaborative growth of high-reaction kinetics composite homogeneous core-shell heterostructure between various materials is innovatively proposed with different structures in one step. The NiCo-LDH and PPy successfully symbiotically grow on activated carbon fiber fabric in one step. The open channel structure of the NiCo-LDH nanosheets is preserved while PPy effectively wrapped around the NiCo-LDH. The well-defined nanostructure with abundant active sites and convenient ion diffusion paths is favorable for electrolyte entry into the entire nanoarrays. In addition, owing to the enhanced electronic interaction between different components through XPS analysis, the NiCo-LDH@PPy electrode shows outstanding reaction kinetics and structural stability. The as-synthesized NiCo-LDH@PPy exhibited excellent super-capacitive storage capabilities, robust capacitive activity, and good rate survival. Furthermore, an asymmetric supercapacitor (ASC) device made of NiCo-LDH@PPy and activated carbon (AC) is able to maintain a long cycle life while achieving high power and energy densities.

Advances in Mn-Based MOFs and Their Derivatives for High-Performance Supercapacitor

As the most widely used metal material in supercapacitors, manganese (Mn)-based materials possess the merits of high theoretical capacitance, stable structure as well as environmental friendliness. However, due to poor conductivity and easy accumulation, the practical capacitance of Mn-based materials is far lower than that of theoretical value. Therefore, accurate structural adjustment and controllable strategies are urgently needed to optimize the electrochemical properties of Mn-based materials. Metal-organic frameworks (MOFs) are porous materials with high specific surface area (SSA), tunable pore size, and controllable structure. These features make them attractive as precursors or scaffold for the synthesis of metal-based materials and composites, which are important for electrochemical energy storage applications. Therefore, a timely and comprehensive review on the classification, design, preparation and application of Mn-based MOFs and their derivatives for supercapacitors has been given in this paper. The recent advancement of Mn-based MOFs and their derivatives applied in supercapacitor electrodes are particularly highlighted. Finally, the challenges faced by Mn-MOFs and their derivatives for supercapacitors are summarized, and strategies to further improve their performance are proposed. The aspiration is that this review will serve as a beneficial compass, guiding the logical creation of Mn-based MOFs and their derivatives in the future.

Silicon carbide single crystals for high-temperature supercapacitors

Designing advanced electrode materials that can be reliably cycled at high temperatures and used for assembling advanced energy storage devices remain a major challenge. As a representative of novel wide bandgap semiconductors, silicon carbide (SiC) single crystals have broad prospects in high-temperature energy storage due to their excellent characteristics such as low thermal expansion coefficient, high temperature radiation resistance and stable chemical properties. In this work, an N-type SiC single-crystal material with a high-density porous structure was successfully designed and prepared by using an improved electrochemical anodic oxidation strategy. Besides, the N-type SiC single crystals were used in electrochemical energy storage as an integrated electrode material, exhibiting superior electrochemical performance. In addition, the high-temperature supercapacitor device assembled with ionic liquids has a wide operating temperature range and maintains a capacity of 88.24% after 5000 cycles at 150 °C. The reasons for its high energy storage performance are discussed through electrochemical tests and first-principles calculation methods. This study proves that the application of SiC single crystals in supercapacitor devices has great potential in the field of high-temperature energy storage, providing a reference for the further development of novel semiconductors in the field of energy storage and optoelectronic devices.

PEDOT:Nafion for Highly Efficient Supercapacitors

Supercapacitors offer notable properties as energy storage devices, providing high power density and fast charging and discharging while maintaining a long cycling lifetime. Although poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) has become a gold standard among organic electronics materials, researchers are still investigating ways to further improve its capacitive characteristics. In this work, we introduced Nafion as an alternative polymeric counterion to PSS to form highly capacitive PEDOT/Nafion; its advantageous supercapacitive properties were further improved by treatment with either dimethyl sulfoxide or ethylene glycol. Accordingly, electrochemical characterization of PEDOT/Nafion films revealed their high areal capacitance (22 mF cm-2 at 10 mV/s) and low charge transfer resistance (∼380 Ω), together with excellent volumetric capacitance (74 F cm-3), Coulombic efficiency (99%), and an energy density of 23.1 ± 1.5 mWh cm-3 at a power density of 0.5 W cm-3, resulting from a more effective ion diffusion inside the conductive film, as confirmed by the results of spectroscopic studies. A proof-of-concept symmetric supercapacitor based on PEDOT/Nafion was characterized with a specific capacitance of approximately 15.7 F g-1 and impressive long-term stability (Coulombic efficiency ∼99% and capacitance ∼98.7% after 1000 charging/discharging cycles), overperforming the device based on PEDOT/PSS.

Chemical synthesis and super capacitance performance of novel CuO@Cu4O3/rGO/PANI nanocomposite electrode

Copper oxide-based nanocomposites are promising electrode materials for high-performance supercapacitors due to their unique properties that aid electrolyte access and ion diffusion to the electrode surface. Herein, a facile and low-cost synthesis in situ strategy based on co-precipitation and incorporation processes of reduced graphene oxide (rGO), followed by in situ oxidative polymerization of aniline monomer has been reported. CuO@Cu4O3/rGO/PANI nanocomposite revealed the good distribution of CuO@Cu4O3 and rGO within the polymer matrix which allows improved electron transport and ion diffusion process. Galvanostatic charge-discharge (GCD) results displayed a higher specific capacitance value of 508 F g-1 for CuO@Cu4O3/rGO/PANI at 1.0 A g-1 in comparison to the pure CuO@Cu4O3 278 F g-1. CuO@Cu4O3/rGO/PANI displays an energy density of 23.95 W h kg-1 and power density of 374 W kg-1 at the current density of 1 A g-1 which is 1.8 times higher than that of CuO@Cu4O3 (13.125 W h kg-1) at the same current density. The retention of the electrode was 93% of its initial capacitance up to 5000 cycles at a scan rate of 100 mV s-1. The higher capacitance of the CuO@Cu4O3/rGO/PANI electrode was credited to the formation of a fibrous network structure and rapid ion diffusion paths through the nanocomposite matrix that resulted in enhanced surface-dependent electrochemical properties.

3D net-like Co3O4@NiO nanostructures for high performance supercapacitors

Co3O4@NiO composite electrode materials were successfully synthesized by a two-step hydrothermal method followed by annealing treatment. Due to their three-dimensional network structure, these composite materials exhibited a large specific surface area, enhancing their electrochemical performance. Consequently, the Co3O4@NiO electrode demonstrated a specific capacitance of 1306 F g-1 at a current density of 1 A g-1, an excellent specific capacitance retention rate of 95.5% after 3000 cycles even at 8 A g-1 and a coulombic efficiency approaching 100%. These outstanding properties make the Co3O4@NiO composite materials promising electrode materials for high performance supercapacitors.

Experimental and Theoretical Insights into Interfacial Properties of 2D Materials for Selective Water Transport Membranes: A Critical Review

Interfacial properties, such as wettability and friction, play critical roles in nanofluidics and desalination. Understanding the interfacial properties of two-dimensional (2D) materials is crucial in these applications due to the close interaction between liquids and the solid surface. The most important interfacial properties of a solid surface include the water contact angle, which quantifies the extent of interactions between the surface and water, and the water slip length, which determines how much faster water can flow on the surface beyond the predictions of continuum fluid mechanics. This Review seeks to elucidate the mechanism that governs the interfacial properties of diverse 2D materials, including transition metal dichalcogenides (e.g., MoS2), graphene, and hexagonal boron nitride (hBN). Our work consolidates existing experimental and computational insights into 2D material synthesis and modeling and explores their interfacial properties for desalination. We investigated the capabilities of density functional theory and molecular dynamics simulations in analyzing the interfacial properties of 2D materials. Specifically, we highlight how MD simulations have revolutionized our understanding of these properties, paving the way for their effective application in desalination. This Review of the synthesis and interfacial properties of 2D materials unlocks opportunities for further advancement and optimization in desalination.

Polyaniline-graphene based composites electrode materials in supercapacitor: synthesis, performance and prospects

Supercapacitors (SCs) have become one of the most popular energy-storage devices for high power density and fast charging/discharging capability. Polyaniline is a class of conductive polymer materials with ultra-high specific capacitance, and the excellent mechanical properties will play a key role in the research of flexible SCs. The synergistic effect between polyaniline and graphene is often used to overcome their respective inherent shortcomings, thus the high-performance polyaniline-graphene based nanocomposite electrode materials can be prepared. The development of graphene-polyaniline nanocomposites as electrode materials for SCs depends on their excellent microstructure design. However, it is still difficult to seek a balance between graphene performance and functionalization to improve the weak interfacial interaction between graphene and polyaniline. In this manuscript, the latest preparation methods, research progress and research results of graphene-polyaniline nanocomposites on SCs are reviewed, and the optimization of electrode structures and performances is discussed. Finally, the prospect of graphene-polyaniline composites is expected.

Montmorillonite/Poly(Pyrrole) for Low-Cost Supercapacitor Electrode Hybrid Materials

Conductive polymers such as polypyrrole have been widely used as pseudo-capacitive electrodes for supercapacitors. This work demonstrates a simple method to improve the performance of conductive polymer electrodes by adding montmorillonite in order to perform capacitive behavior. Conductive composite polymers (CCPs) based on montmorillonite/polypyrrole (MMT/PPy(Cl)) have been synthesized by polymerization using FeCl3 as an oxidizing agent. During the preparation of CCP, the effect of MMT/pyrrole mass ratio and the influence of the amount of added H+ and temperature of the synthesis medium on the electrochemical performance of the composite have been investigated. The investigation associated with conductivity measurement allowed us to determine the best conditions to reach a high specific capacitance of 465 F gr-1 measured by cyclic voltammetry with respect to the CCP synthesized at ambient temperature (220 F gr-1) and a 35% increase in capacity compared to its homologue synthesized in neutral conditions at a low temperature. These performances have been advantageously correlated both to the edge acidity of the host material and to the evolution of its conductivity according to the preparation conditions. The galvanostatic charge/discharge tests also confirm the stability of the obtained composite, and a capacitance of 325 F g-1 for the best CCP is recorded with a regime of 1 A g-1. In addition, the durability of the device shows that the proposed material has a relatively good stability during cycling.

Rapid Near-Patient Impedimetric Sensing Platform for Prostate Cancer Diagnosis

With the global escalation of concerns surrounding prostate cancer (PCa) diagnosis, reliance on the serologic prostate-specific antigen (PSA) test remains the primary approach. However, the imperative for early PCa diagnosis necessitates more effective, accurate, and rapid diagnostic point-of-care (POC) devices to enhance the result reliability and minimize disease-related complications. Among POC approaches, electrochemical biosensors, known for their amenability and miniaturization capabilities, have emerged as promising candidates. In this study, we developed an impedimetric sensing platform to detect urinary zinc (UZn) in both artificial and clinical urine samples. Our approach lies in integrating label-free impedimetric sensing and the introduction of porosity through surface modification techniques. Leveraging a cellulose acetate/reduced graphene oxide composite, our sensor's recognition layer is engineered to exhibit enhanced porosity, critical for improving the sensitivity, capture, and interaction with UZn. The sensitivity is further amplified by incorporating zincon as an external dopant, establishing highly effective recognition sites. Our sensor demonstrates a limit of detection of 7.33 ng/mL in the 0.1-1000 ng/mL dynamic range, which aligns with the reference benchmark samples from clinical biochemistry. Our sensor results are comparable with the results of inductively coupled plasma mass spectrometry (ICP-MS) where a notable correlation of 0.991 is achieved. To validate our sensor in a real-life scenario, tests were performed on human urine samples from patients being investigated for prostate cancer. Testing clinical urine samples using our sensing platform and ICP-MS produced highly comparable results. A linear correlation with R2 = 0.964 with no significant difference between two groups (p-value = 0.936) was found, thus confirming the reliability of our sensing platform.

Morphological control and performance engineering of Co-based materials for supercapacitors

As one of the most promising energy storage devices, supercapacitors exhibit a higher power density than batteries. However, its low energy density usually requires high-performance electrode materials. Although the RuO2 material shows desirable properties, its high cost and toxicity significantly limit its application in supercapacitors. Recent developments demonstrated that Co-based materials have emerged as a promising alternative to RuO2 for supercapacitors due to their low cost, favorable redox reversibility and environmental friendliness. In this paper, the morphological control and performance engineering of Co-based materials are systematically reviewed. Firstly, the principle of supercapacitors is briefly introduced, and the characteristics and advantages of pseudocapacitors are emphasized. The special forms of cobalt-based materials are introduced, including 1D, 2D and 3D nanomaterials. After that, the ways to enhance the properties of cobalt-based materials are discussed, including adding conductive materials, constructing heterostructures and doping heteroatoms. Particularly, the influence of morphological control and modification methods on the electrochemical performances of materials is highlighted. Finally, the application prospect and development direction of Co-based materials are proposed.

Construction and application of NiCo2O4@MnS composite with hierarchical structure for hybrid supercapacitor

The development of an electrochemical energy storage system with exceptional performance is an important way to address the energy crisis and environmental pollution of the modem world. In this study, an NiCo2O4@MnS composite with a unique hierarchical structure has been successfully synthesized on an NF substrate using the hydrothermal-electrodeposition method. The results indicate that NiCo2O4@MnS possesses superior specific capacitance and excellent cycling stability. At a current density of 2 A g-1, its specific capacitance can reach 2100 F g-1, while the capacitance retention is still 76% after 10 000 cycles at 10 A g-1. Moreover, when the current density is 1 A g-1, the assembled NiCo2O4@MnS//AC device can deliver a specific capacitance of 203 F g-1, and the energy density is up to 55 W h kg-1 at a power density of 697 W kg-1. These outstanding electrochemical properties of NiCo2O4@MnS can be ascribed to the increase in ion diffusion, specific surface area and electronic conductivity due to its unique hierarchical structure and introduction of MnS.

Effect of annealing temperature on structural and electrochemical behaviour on MgFe2O4as electrode material in neutral aqueous electrolyte for supercapacitors

Binary metal oxides possess unique structures and multiple oxidation states, making them highly valuable in electrochemical analysis. This study aims to determine the effect of annealing temperature on the electrochemical properties of magnesium ferrite when used as an electrode material in a neutral aqueous electrolyte. We utilized the sol-gel technique to synthesize the material and annealed it at various temperatures. Our analysis of the material using different characterization techniques reveals significant changes in its structural and electrochemical properties. We found that the material exhibited a range of phases, and higher annealing temperatures led to improved electrochemical properties. The electrochemical measurements showed reversible and redox pseudo-capacitance behavior, with the material annealed at 500 °C exhibiting the highest specific capacitance of 117 F g-1at a current density of 0.5 A g-1. Capacitive and diffusion-controlled processes govern the total charge storage mechanism, and their contribution changes significantly as the annealing temperature varies. The capacitance retention of 500 °C annealed sample was 58% and it remained stable. This work establishes a correlation between annealing temperature on structural, morphological, and electrochemical behavior, thereby opening up avenues for tailoring them effectively. These findings can be useful in the development of future electrode materials for electrochemical applications.

Preparation and research progress of lignin-based supercapacitor electrode materials

The reserve of lignin in the biological world is the second largest biomass resource after cellulose. Lignin has the characteristics of wide sources, low cost, and rich active components. Due to environmental pollution and energy scarcity, lignin is often used as a substitute good for petrochemical products. Lignin-based functional materials can be prepared by chemical modification or compounding, which are widely used in the fields of energy storage, chemical industry, and medicine. Among them, lignin-based carbon materials have the features of stable chemical properties, large pH application range, ideal electrical conductivity, developed pore size, and high specific surface area, which have great application prospects as supercapacitor materials. This paper mainly introduces the structural properties of lignin, the methods, and mechanisms of carbonization, pore-making, and pore-expansion, as well as the research progress of lignin-based carbon materials for supercapacitors, while looking forward to the future research direction of lignin carbon materials.

Advanced Functionalized Materials Based on Layer-by-Layer Assembled Natural Cellulose Nanofiber for Electrodes: A Review

The depletion of fossil fuel resources and its impact on the environment provide a compelling motivation for the development of sustainable energy sources to meet the increasing demand for energy. Accordingly, research and development of energy storage devices have emerged as a critical area of focus. The electrode materials are critical in the electrochemical performance of energy storage devices, such as energy storage capacity and cycle life. Cellulose nanofiber (CNF) represents an important substrate with potentials in the applications of green electrode materials due to their environmental sustainability and excellent compatibility. By utilizing the layer-by layer (LbL) process, well-defined nanoscale multilayer structure is prepared on a variety of substrates. In recent years, increasing attention has focused on electrode materials produced from LbL process on CNFs to yield electrodes with exceptional properties, such as high specific surface area, outstanding electrical conductivity, superior electrochemical activity, and exceptional mechanical stability. This review provides a comprehensive overview on the development of functional CNF via the LbL approach as electrode materials.

The Need for Smart Materials in an Expanding Smart World: MXene-Based Wearable Electronics and Their Advantageous Applications

As a result of the transformation of inflexible electronic structures into flexible and stretchy devices, wearable electronics now provide great advantages in a variety of fields, including mobile healthcare sensing and monitoring, human-machine interfaces, portable energy storage and harvesting, and more. Because of their enriched surface functionalities, large surface area, and high electrical conductivity, transition metal nitrides and carbides (also known as MXenes) have recently come to be extensively considered as a group of functioning two-dimensional nanomaterials as well as exceptional fundamental elements for forming flexible electronics devices. This Review discusses the most recent advancements that have been made in the field of MXene-enabled flexible electronics for wearable electronics. The emphasis is placed on extensively established nonstructural features in order to highlight some MXene-enabled electrical devices that were constructed on a nanometric scale. These attributes include devices configured in three dimensions: printed materials, bioinspired structures, and textile and planar substrates. In addition, sample applications in electromagnetic interference (EMI) shielding, energy, healthcare, and humanoid control of machinery illustrate the exceptional development of these nanodevices. The increasing potential of MXene nanoparticles as a new area in next-generation wearable electronic technologies is projected in this Review. The design challenges associated with these electronic devices are also discussed, and possible solutions are presented.

Production of Large Specific Capacitance by Electrodes with Low Active Mass and Synergistic Mechanisms

Decoration of vanadium nitride nanoparticles on carbon nanotubes creates electrodes with three different energy storage mechanisms that operate synergistically to give a high specific capacitance with a low active mass. Calculation and measurements further indicate the power and energy density to be as high as 105-106 W/kg and 102 Wh/kg, respectively. Particle attachment also greatly improves the capacitive coefficient, including ionic transmittance, charge transfer, porosity, and conductivity. Corrosion tests based on the Tafel method reveal the corrosion potential and current of electrodes as low as -0.721 V and 7.53 × 10-4 A, respectively.

One-Step Fabrication of Integrated Graphene/Polypyrrole/Carbon Cloth Films for Supercapacitor Electrodes

The facile and cost-effective preparation of supercapacitor electrodes is significant for the application of this kind of electrochemical energy-storing module. In this work, we designed a feasible strategy to fabricate a binary active material onto a current collector in one step. A colloidal mixture of graphene oxide and pyrrole layered on a carbon cloth could undergo a redox reaction through a mild hydrothermal process to yield a reduced graphene oxide/polypyrrole hydrogel film anchored onto the carbon cloth. The integrated electrode with the porous graphene/polypyrrole active material could be directly utilized as a freestanding working electrode for electrochemical measurements and the assembly of supercapacitor devices. The as-prepared electrode could achieve a high capacitance of 1221 mF cm-2 at 1 mA cm-2 (531 F g-1) with satisfactory cycling stability. The constructed symmetric supercapacitor with two optimal electrodes could provide an energy density of 70.4 μWh cm-2 (15.3 Wh kg-1). This work offers a feasible pathway toward the integration of graphene/conducting polymer composites as electrochemical electrodes.

Effect of synthesis methods on the activity of NiO/Co3O4 as an electrode material for supercapacitor: in the light of X-ray diffraction study

The formation of heterostructures by combining individual components (NiO and Co3O4) is a preferred approach to enhance electrochemical performance as it leads to improved charge transfer and surface reaction kinetics. In the present work, a NiO/Co3O4 composite was prepared by two methods. First, neat NiO and Co3O4 were prepared by adopting the hydrothermal method followed by the formation of the composite (i) by a hydrothermal route (NC-Hydro) and (ii) by a calcination route (NC-Cal). NC-Hydro composite shows a specific capacity of 176 C g-1 at 1 A g-1 of current density in the three-electrode system in a 2 M KOH solution as an electrolyte with 90% cyclic retention after 5000 cycles at 4 A g-1. NC-Cal shows a specific capacity of 111 C g-1 at 1 A g-1 with 75% cyclic retention. The coulombic efficiency of NC-Hydro was 86.3% while for NC-Cal it was 42.3%. The reason behind the superior electrochemical performance of NC-Hydro in comparison to NC-Cal may be the large interlayer spacing and lattice parameters of the former, which provide large space for redox reactions. The unit cell volume of the composites was more than that of the constituents. This study reveals that the composites prepared by the hydrothermal method have superior electrochemical properties in comparison to composites prepared by the calcination method.

Recent Advancements in Electrochemical Hydrogen Production via Hybrid Water Splitting

As one of the most promising approaches to producing high-purity hydrogen (H2 ), electrochemical water splitting powered by the renewable energy sources such as solar, wind, and hydroelectric power has attracted considerable interest over the past decade. However, the water electrolysis process is seriously hampered by the sluggish electrode reaction kinetics, especially the four-electron oxygen evolution reaction at the anode side, which induces a high reaction overpotential. Currently, the emerging hybrid electrochemical water splitting strategy is proposed by integrating thermodynamically favorable electro-oxidation reactions with hydrogen evolution reaction at the cathode, providing a new opportunity for energy-efficient H2 production. To achieve highly efficient and cost-effective hybrid water splitting toward large-scale practical H2 production, much work has been continuously done to exploit the alternative anodic oxidation reactions and cutting-edge electrocatalysts. This review will focus on recent developments on electrochemical H2 production coupled with alternative oxidation reactions, including the choice of anodic substrates, the investigation on electrocatalytic materials, and the deep understanding of the underlying reaction mechanisms. Finally, some insights into the scientific challenges now standing in the way of future advancement of the hybrid water electrolysis technique are shared, in the hope of inspiring further innovative efforts in this rapidly growing field.

Telluride-Based Materials: A Promising Route for High Performance Supercapacitors

As supercapacitor (SC) technology continues to evolve, there is a growing need for electrode materials with high energy/power densities and cycling stability. However, research and development of electrode materials with such characteristics is essential for commercialization the SC. To meet this demand, the development of superior electrode materials has become an increasingly critical step. The electrochemical performance of SCs is greatly influenced by various factors such as the reaction mechanism, crystal structure, and kinetics of electron/ion transfer in the electrodes, which have been challenging to address using previously investigated electrode materials like carbon and metal oxides/sulfides. Recently, tellurium and telluride-based materials have garnered increasing interest in energy storage technology owing to their high electronic conductivity, favorable crystal structure, and excellent volumetric capacity. This review provides a comprehensive understanding of the fundamental properties and energy storage performance of tellurium- and Te-based materials by introducing their physicochemical properties. First, we elaborate on the significance of tellurides. Next, the charge storage mechanism of functional telluride materials and important synthesis strategies are summarized. Then, research advancements in metal and carbon-based telluride materials, as well as the effectiveness of tellurides for SCs, were analyzed by emphasizing their essential properties and extensive advantages. Finally, the remaining challenges and prospects for improving the telluride-based supercapacitive performance are outlined.

Conjugated Polyelectrolyte Thin Films for Pseudocapacitive Applications

A subclass of organic semiconductors known as conjugated polyelectrolytes (CPEs) is characterized by a conjugated backbone with ionic pendant groups. The water solubility of CPEs typically hinders applications of thin films in aqueous media. Herein, it is reported that films of an anionic CPE, namely CPE-K, drop cast from water produces single-component solid-state pseudocapacitive electrodes that are insoluble in aqueous electrolyte. That X-ray diffraction experiments reveal a more structurally ordered film, relative to the as-obtained powder from chemical synthesis, and dynamic light scattering measurements show an increase in aggregate particle size with increasing [KCl] indicate that CPE-K films are insoluble because of tight interchain contacts and electrostatic screening by the electrolyte. CPE-K film electrodes can maintain 85% of their original capacitance (84 F g-1 ) at 500 A g-1 and exhibit excellent cycling stability, where a capacitance retention of 93% after 100 000 cycles at a current density of 35 A g-1 . These findings demonstrate that it is possible to use initially water soluble ionic-organic materials in aqueous electrolytes, by increasing the electrolyte concentration. This strategy can be applied to the application of conjugated polyelectrolytes in batteries, organic electrochemical transistors, and electrochemical sensors, where fast electron and ion transport are required.

High Energy Density Supercapacitors: An Overview of Efficient Electrode Materials, Electrolytes, Design, and Fabrication

Supercapacitors (SCs) are potentially trustworthy energy storage devices, therefore getting huge attention from researchers. However, due to limited capacitance and low energy density, there is still scope for improvement. The race to develop novel methods for enhancing their electrochemical characteristics is still going strong, where the goal of improving their energy density to match that of batteries by increasing their specific capacitance and raising their working voltage while maintaining high power capability and cutting the cost of production. In this light, this paper offers a succinct summary of current developments and fresh insights into the construction of SCs with high energy density which might help new researchers in the field of supercapacitor research. From electrolytes, electrodes, and device modification perspectives, novel applicable methodologies were emphasized and explored. When compared to conventional SCs, the special combination of electrode material/composites and electrolytes along with their fabrication design considerably enhances the electrochemical performance and energy density of the SCs. Emphasis is placed on the dynamic and mechanical variables connected to SCs' energy storage process. To point the way toward a positive future for the design of high-energy SCs, the potential and difficulties are finally highlighted. Further, we explore a few important topics for enhancing the energy densities of supercapacitors, as well as some links between major impacting factors. The review also covers the obstacles and prospects in this fascinating subject. This gives a fundamental understanding of supercapacitors as well as a crucial design principle for the next generation of improved supercapacitors being developed for commercial and consumer use.

Turning Complexity into Simplicity: In Situ Synthesis of High-Performance Si@C Anode in Battery Manufacturing Process by Partially Carbonizing the Slurry of Si Nanoparticles and Dual Polymers

For Si/C anodes, achieving excellent performance with a simple fabrication process is still an ongoing challenge. Herein, we report a green, facile and scalable approach for the in situ synthesis of Si@C anodes during the electrode manufacturing process by partially carbonizing Si nanoparticles (Si NPs) and dual polymers at a relatively low temperature. Due to the proper mass ratio of the two polymer precursors and proper carbonization temperature, the resultant Si-based anode demonstrates a typical Si@C core-shell structure and has strong mechanical properties with the aid of dual-interfacial bonding between the Si NPs core and carbon shell layer, as well as between the C matrix and the underlying Cu foil. Consequently, the resultant Si@C anode shows a high specific capacity (3458.1 mAh g-1 at 0.2 A g-1), good rate capability (1039 mAh g-1 at 4 A g-1) and excellent cyclability (77.94% of capacity retention at a high current density of 1 A g-1 after 200 cycles). More importantly, the synthesis of the Si@C anode is integrated in situ into the electrode manufacturing process and, thus, significantly decreases the cost of the lithium-ion battery but without sacrificing the electrochemical performance of the Si@C anode. Our results provide a new strategy for designing next-generation, high-capacity and cost-effective batteries.