Electrochemical Hydrogen Production Coupling with the Upgrading of Organic and Inorganic Chemicals

Electrocatalytic water splitting powered by renewable energy is a green and sustainable method for producing high-purity H2. However, in conventional water electrolysis, the anodic oxygen evolution reaction (OER) involves a four-electron transfer process with inherently sluggish kinetics, which severely limits the overall efficiency of water splitting. Recently, replacing OER with thermodynamically favorable oxidation reactions, coupled with the hydrogen evolution reaction, has garnered significant attention and achieved remarkable progress. This strategy not only offers a promising route for energy-saving H₂ production but also enables the simultaneous synthesis of high-value-added products or the removal of pollutants at the anode. Researchers successfully demonstrate the upgrading of numerous organic and inorganic alternatives through this approach. In this review, the latest advances in the coupling of electrocatalytic H2 production and the upgrading of organic and inorganic alternative chemicals are summarized. What's more, the optimization strategy of catalysts, structure-performance relationship, and catalytic mechanism of various reactions are well discussed in each part. Finally, the current challenges and future prospects in this field are outlined, aiming to inspire further innovative breakthroughs in this exciting area of research.

Phase-dependent optical, photocatalytic and capacitive properties of tungsten oxide nanowires

Transition metal oxides hold great promise across a wide range of applications due to favorable properties such as high abundance, low toxicity, and excellent stability. Nanoengineering approaches are essential for controlling the structural, optical, and electronic properties of these materials, enabling the achievement of desired characteristics in a cost-effective and environmentally friendly manner. In this study, we synthesize stoichiometric (WO3) and sub-stoichiometric (WO3-x) tungsten oxide nanowires by controlling their phases and morphologies through the hydrothermal method. This approach allows us to systematically investigate the effects of different phases and oxygen vacancies on the optical properties, as well as on photocatalytic and supercapacitance applications. We use the photodegradation of RhB as a benchmark for photocatalytic activity under various experimental conditions, revealing that oxygen vacancies significantly influence photocatalytic behavior. For example, WO3-x nanowires adsorb/degrade a substantial amount of RhB within short durations under ambient conditions, where WO3 nanowires are mostly inactive. The addition of H2O2 enhances the photocatalytic performance of WO3 nanowires over 30 minutes, with even better results under low pH conditions with H2O2. This study also explores the phase-dependent electrochemical properties of WO3 and WO3-x nanowires, providing insights into their potential for improved supercapacitor performance by leveraging their complementary properties in symmetric and asymmetric configurations. WO3-x, with a higher density of oxygen vacancies and thinner structure, offers enhanced conductivity and increased active sites for charge storage, resulting in superior specific capacitance and charge retention.

Electrochemical synthesis and supercapacitor performance of manganese and cerium oxide-doped polyaniline composites

In this study, polyaniline-based conductive polymers doped with manganese oxide and cerium oxide were electrochemically synthesized for the first time. Unlike previous studies, manganese oxide and cerium oxide doped polyaniline synthesis was carried out in perchloric acid. The resulting composite materials were characterized using spectroscopic and microscopic techniques. The doped polyaniline composites were employed as electrode components in supercapacitors and analyzed using cyclic voltammetry and electrochemical impedance spectroscopy. Changes in capacitive behavior over cycling were examined via galvanostatic charge-discharge measurements. The areal capacitance of the cerium oxide and manganese oxide doped polyaniline electrodes, synthesized under optimal conditions, were measured as 950 mF cm-2and 660 mF cm-2, respectively, at a charge-discharge current of 10 mA cm-2.

Biomass-Based Sustainable Graphene for Advanced Electronic Technology: A Review

Through its remarkable mechanical, electrical, and thermal qualities, graphene has become a revolutionary material in electronics. Sustainable graphene synthesis from biomass residues offers a possible path toward adhering to the demand for economical and ecologically friendly graphene production methods. The present study thoroughly examines the numerous biomass sources used for graphene synthesis, such as plant-derived materials, agricultural waste, and other organic leftovers. The benefits and drawbacks of several synthesis methods are examined, including pyrolysis, chemical exfoliation, and hydrothermal carbonization. The study also explores the possible uses of graphene produced from biomass in electronics, including sensors, energy storage devices, electronic devices with flexibility, and electromagnetic interference (EMI) shielding. This review highlights how biomass-based graphene can revolutionize the electronics sector by bridging the gap between electronic applications, synthesis techniques, and biomass supplies.

Ultrahigh-Surface Area Hierarchically Porous Carbon Derived From Sweet Potato Extraction Residue-Syrup for High Performance Supercapacitor

Converting biomass waste into value-added products is desirable and a major goal for the circular economy. Herein, the agricultural waste and sweet potato extraction residues (SPR) were converted into hierarchially porous carbons (HPCs) by a facile method using KOH as the activation agent. The as-obtained SPR-HPCs exhibited a well developed pore structure and very high specific surface area (SSA). By controlling the fabrication conditions including the dosage of KOH and activation temperature, the optimized SPR-HPC-3.5-800 had an ultrahigh SSA of 3206 m2 g-1 with high pore volume of 2.132 cm3 g-1. When used as electrode materials, the electrochemical studies demonstrated that the SPR-HPC-3.5-800 based electrode achieved high specific capacitance of 320 F g-1 at a current density of 0.5 A g-1 and the symmetrical supercapacitor in 6 M KOH achieved energy density of 6.8 Wh kg-1 at 249 W kg-1. Furthermore, high electrochemical stability was achieved for the SPR-HPCs. This study provides a good example of the production of value-added products from biowastes.

Cerium oxide nanoparticles decorated on graphene oxide nanosheets as battery-type cathode material for supercapacitors

Designing advanced materials that effectively mitigate the poor cycle life of battery-type electrodes with high specific capacities is crucial for next-generation energy storage systems. Herein, graphene oxide-ceria (GO-CeO2) nanocomposite synthesized via a facile wet chemical route is explored as cathode for high-performance supercapacitors. The morphological analysis suggests fine ceria (CeO2) nanoparticles dispersed over ultrathin graphene oxide (GO) sheets while structural studies reveal face-centered cubic phase of CeO2 in the nanocomposite. In-depth electrochemical performance investigation of the nanocomposite in 6 M KOH aqueous electrolyte demonstrated its excellent battery-type behavior with least ion diffusion resistance and a superior cycle life resulting from the synergistic effect of redox-active CeO2 and 2D GO with abundant oxygen functionalities. Specifically, GO-CeO2 composite electrode delivered a maximum specific capacitance of 625.9 F/g (52.2 mAh/g) at 3 A/g current density, which is substantially higher than the capacitance values obtained for GO and CeO2 electrodes, and demonstrated an excellent cycling stability with ∼ 100 % capacitance retention after 10,000 CV cycles. Furthermore, a novel aqueous asymmetric supercapacitor (ASC) is explored with GO-CeO2 as positive and iron(III) oxyhydroxide (FeOOH) as negative electrode material in 6 M KOH electrolyte which has also displayed good energy-power density combination along with excellent cycle stability. The study thus endorses rational design of nanocomposite materials with suitable functionalities as an excellent strategy in augmenting the performance of futuristic energy storage devices.

Supercapacitor Materials Database Generated using Web Scrapping and Natural Language Processing

Electrochemical energy storage plays a vital role in achieving environmental sustainability. Supercapacitors emerge as promising alternatives to batteries due to their high-power density and extended lifespan. Extensive scholarly research has been conducted on supercapacitor energy storage, providing valuable insights into materials and performance parameters. This study presents a comprehensive supercapacitor materials database, created by web scraping the article abstracts from the Scopus database and processing them using Regular Expressions, the BatteryBERT Language Model, and the ChemDataExtractor Python package. The final database comprises 28,269 recorded entries across 21 relevant fields, including metadata, electrode and electrolyte materials, and seven key device performance parameters. This initiative aims to establish a novel database that can support the prediction and design of advanced supercapacitors.

Facile Synthesis of 3D NC-rGO@Ni-Foam Nanonetwork as a Binder-Free Hybrid Electrode Material for Ultrahigh Capacitance Applications

In this study, a three-dimensional (3D) structured nanomaterial has been developed to enhance the electrochemical properties of supercapacitors. The nanomaterial's structure was engineered by incorporating divalent metal ions (M2+: Ni2+ and Co2+) into reduced graphene oxide (rGO) layers supported on nickel foam (3D NC-rGO@Ni-foam), forming a binder-free hybrid electrode. This was accomplished through a combination of in situ wet-chemistry and hydrothermal techniques. This binder-free electrode material has stacked layers of rGO, which improve conductivity, while the M2+ ions intercalated between these layers function as redox couples, thereby significantly improving the specific capacitance. Furthermore, the Ni-foam substrate offers a porous configuration and works as the current collector. In contrast to traditional slurry coating methods, the in situ growth of nanostructures on Ni-foam is expected to enhance strong adhesion, high conductivity, and effective ion transport. The structural morphology, chemical composition, and electrochemical behavior of the 3D NC-rGO@Ni-foam electrode were comprehensively investigated using techniques such as scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and other analytical methods. This binder-free 3D hybrid electrode material demonstrated a specific capacitance (C s) of 2612 F/g at 1 A/g. The symmetric device fabricated also demonstrated a substantial energy density (E) of 55 W·h/kg and a power density (P) of 155 W/kg across a wide potential window of 2.5 V. The electrochemical characteristics and mechanical stability of 3D NC-rGO@Ni-foam indicate its potential as a high-performance electrode material for scalable energy storage systems.

Unveiling the Robustness: Comprehensive Analysis of Plastic Chip Electrode Stability in Diverse Environments

Plastic chip electrode (PCE) is a polymer composite electrode recognized for its scalability, versatility, and cost-effectiveness. PCE features a self-standing structure, bulk conductivity, and a straightforward fabrication process. This multipurpose electrode has been widely used in various applications, including anodic stripping voltammetry, electrocatalysis for water splitting, electrochemical sensors, and electrowinning, often under extreme conditions. Therefore, understanding the stability of PCE across a broad range of conditions is crucial. This study systematically examines the corrosion behaviors and chemical resistance of PCE across the entire pH range (1-14), in seawater (SW) and in industrial effluent (IE). Electrochemical corrosion behaviors were assessed using Tafel polarization studies, while field emission scanning electron microscopy (FE-SEM) was utilized to investigate pitting behaviors and surface morphology. X-ray photoelectron spectroscopy (XPS) was employed to analyze surface functionalities to assess the practical applicability of the treated electrodes. The long-term stability of the electrode in seawater, along with its mechanical robustness, has also been evaluated. This comprehensive analysis provides valuable insights into the robustness and potential applications of PCE in diverse and challenging environments.

Research Progress on Microwave Synthesis of 3d Transition Metal (Mn, Fe, Co, and Ni) Oxide Nanomaterials for Supercapacitors

3d transition metal oxides composed of Mn, Fe, Co, and Ni have emerged as promising candidates for supercapacitor electrode materials due to their high theoretical specific capacitance, abundant redox-active sites, variable oxidation states, environmental friendliness, and low cost. Various synthesis strategies have been developed to fabricate these nanostructures, including hydrothermal/solvothermal methods, sol-gel processing, and microwave-assisted synthesis. Among them, microwave irradiation technology, with its rapid heating characteristics and unique thermal/non-thermal effects, offers significant advantages in controlling crystallinity and particle size distribution, suppressing particle agglomeration, and enhancing material purity. Furthermore, microwave effects facilitate the self-assembly and morphological evolution of transition metal oxides, promote the formation of crystal defects, and strengthen interfacial interactions. These effects enable precise microstructural tuning, leading to an increased specific surface area and a higher density of active sites, ultimately enhancing specific capacitance, rate capability, and cycling stability. In recent years, microwave-assisted synthesis has made significant progress in constructing 3d transition metal oxides and their composites, particularly in the development of single-metal and binary-metal oxides, as well as their hybrids with carbon-based materials (e.g., graphene and carbon nanotubes) and other metal oxides. This review systematically summarizes the research progress on microwave-assisted techniques for 3d transition metal oxide-based nanomaterials, with a particular focus on the role of microwave effects in morphology control, interfacial optimization, and electrochemical performance enhancement. Additionally, key challenges in current research are critically analyzed, and potential optimization strategies are proposed. This review aims to provide new insights and perspectives for advancing microwave-assisted synthesis of 3d transition metal oxides in energy storage applications.

High-frequency supercapacitors surpassing dynamic limit of electrical double layer effects

The prosperity of microelectronics has intensified the requirement for miniaturized power systems using capacitors with high capacity and broad frequency ranges. Electrochemical supercapacitors stand out with their superior capacitance density, surpassing traditional electrolytic capacitors by at least two orders of magnitude. However, the intrinsic slow ion dynamics of electrical double layer effects greatly limit supercapacitors characteristic frequency, constraining their applicability in microsystems. This work constructs a near-ideal micro electrochemical supercapacitor, featuring the monolayer graphene as a working electrode, to reveal the ceiling of electrochemical capacitance characteristic frequency. To address this limitation, we introduce a Hybrid Electrochemical Electrolytic Capacitor design, which asymmetrically coupling the electrochemical and dielectric effects. At low frequencies, the electrochemical segment provides sufficient capacity, while its electrolytic segment takes over at high frequencies, broadening the frequency range. Consequently, the hybrid design boasts considerable capacitance density across a broad frequency range. Employing our wafer-scale microfabrication techniques, we showcase a device, achieving a characteristic frequency of 44 kHz and a volume capacitance density of 800 μ F / cm 3 . To demonstrate its practicality in microsystems, the device is integrated with a power management chip and buck circuit module, respectively, with only 2 % space usage compared to commercial electrolytic capacitor, achieving the same performance.

Metal-organic framework glass stabilizes high-voltage cathodes for efficient lithium-metal batteries

The rapid evolution of portable electronics and electric vehicles necessitates batteries with high energy density, robust cycling stability, and fast charging capabilities. High-voltage cathodes, like LiNi0.8Co0.1Mn0.1O2 (NCM-811), promise enhanced energy density but are hampered by poor stability and sluggish lithium-ion diffusion in conventional electrolytes. We introduce a metal-organic framework (MOF) liquid-infusion technique to fully integrate MOF liquid into the grain boundaries of NCM-811, creating a thoroughly coated cathode with a thin, rigid MOF Glass layer. The surface electrically non-conductive MOF Glass layer with 2.9 Å pore windows facilitating Li-ion pre-desolvation and enabling highly aggregative electrolyte formation inside the Glass channels, suppressing solvated Li-ion co-insertion and solvent decomposition. While the inner Glass layer composes of Li-ion conducting components and enhancing fast Li-ion diffusion. This functional structure effectively shields the cathode from particle cracking, CEI rupture, oxygen loss, and transition metal migration. As a result, Li | |Glass@NCM-811 cells demonstrate good rate capability and cycling stability even under high-charge rates and elevated voltages. Furthermore, we also achieve a 385 Wh kg-1 pouch-cell (19.579 g, for pouch-cell), showcasing the practical potential of this method. This straightforward and versatile strategy can be applied to other high-voltage cathodes like Li-rich manganese oxides and LiCoO2.

Ionic liquid assisted construction of synergistic modulated multiphase hybrid composites for boosting electrochemical energy storage

The unique structure and strong interaction of multiphase hybrid materials have garnered significant attention as prospective candidates for electrode materials in the realm of energy storage. The present study presents a rational design of a functional NiSe2-CoSe2/N, B double-doped carbon hybrid composite (NCS/CNB), resulting in the emergence of various novel cooperative regulatory mechanisms involving: (i) the heterogeneous structure of NiSe2 and CoSe2 generates built-in electric fields to increase electron mobility; (ii) the incorporation of polyatomic double-doped carbon (N, and B) expedites electron transfer rate; intriguingly, (iii) ionic liquids not only serve as polyatomic dopants in the reaction system but also influence the microstructure of the composite. Benefiting from these synergistic effects, the NCS/CNB hybrid exhibits remarkable charge storage capacity and rapid electrochemical kinetics, driven by its multi-fold hollow structure and multicomponent cooperative modulation. The capacity (682 C g-1 at 1 A g-1) and rate performance of NCS/CNB surpass those of other monometallic selenides (NiSe2/N, B co-doped carbon (NS/CNB) and CoSe2/N, B co-doped carbon (CS/CNB)) within the same system. In the meantime, an asymmetric device using NCS/CNB as the cathode material performs admirably, displaying an exceptional energy density (51.3 Wh kg-1 at 1.28 kW kg-1). The present research provides valuable perspectives for the innovative design and fabrication of advanced electrode materials exhibiting exceptional electrochemical properties. We firmly believe that hollow structures featuring multiple cooperative regulatory mechanisms and abundant folds will garner significant attention.

Carbon Materials in Voltammetry: An Overview of Versatile Platforms for Antidepressant Drug Detection

This review concentrates on the application of carbon-based materials in the development and fabrication of voltammetric sensors of antidepressant drugs used in the treatment of moderate to severe depression, anxiety disorders, personality disorders, and various phobias. Voltammetric techniques offer outstanding sensitivity and selectivity, accuracy, low detection limit, high reproducibility, instrumental simplicity, cost-effectiveness, and short time of direct determination of antidepressant drugs in pharmaceutical and clinical samples. Moreover, the combination of voltammetric approaches with the unique characteristics of carbon and its derivatives has led to the development of powerful electrochemical sensing tools for detecting antidepressant drugs, which are highly desirable in healthcare, environmental monitoring, and the pharmaceutical industry. In this review, carbon-based materials, such as glassy carbon and boron-doped diamond, and a wide spectrum of carbon nanoparticles, including graphene, graphene oxides, reduced graphene oxides, single-walled carbon nanotubes, and multi-walled carbon nanotubes were described in terms of the sensing performance of agomelatine, alprazolam, amitriptyline, aripiprazole, carbamazepine, citalopram, clomipramine, clozapine, clonazepam, desipramine, desvenlafaxine, doxepin, duloxetine, flunitrazepam, fluoxetine, fluvoxamine, imipramine, nifedipine, olanzapine, opipramol, paroxetine, quetiapine, serotonin, sertraline, sulpiride, thioridazine, trazodone, venlafaxine, and vortioxetine.

High performance supercapacitors driven by the synergy of a redox-active electrolyte and core-nanoshell zeolitic imidazolate frameworks

The selection of appropriate electrolytes plays a crucial role in improving the electrochemical performance of the supercapacitor electrode. The electrolyte helps to select an appropriate potential window of the device, which is directly related to its energy density. Also, the selection of an appropriate electrode material targets the specific capacitance. Therefore, in this work, we targeted an electrode material based on a ZIF-8@ZIF-67 (Z867) core-nanoshell structure and tested its performance in redox active electrolyte (RAE), i.e., 0.2 M K3[Fe(CN)6] in 1 M Na2SO4. The synergy between the core-nanoshell electrode having ZIF-8 as a core and ZIF-67 as a nanoshell along with RAE further complements the redox active sites, resulting in the improved charge transport. Therefore, when the Z867 core-nanoshell electrode is tested in a three-electrode system, it outperforms pristine ZIF-8 and ZIF-67 electrode materials. The working electrode modified with the Z867 core-nanoshell showed a maximum specific capacitance of 496.4 F g-1 at 4.5 A g-1 current density with the RAE, which is much higher than that of the aqueous electrolyte. A Z867-modified working electrode was assembled as the positive and negative electrode in a symmetrical cell configuration to create a redox supercapacitor device for practical application. The constructed device displayed maximal energy and power densities of 49.6 W h kg-1 and 3.2 kW kg-1 respectively, along with a capacitance retention of 92% after 10 000 charge-discharge cycles. Hence, these studies confirm that using RAE can improve the electrochemical performance of electrodes to a greater extent than that of aqueous electrolyte-based supercapacitors.

Conceptualizing Surface-Like Diffusion for Ultrafast Ionic Conduction in Solid-State Materials

Surface-like diffusion is a recently proposed concept to explain the mechanism of ultrafast ionic conduction in high-rate oxide (e. g., niobium oxides and their alloys with TiO2 and WO3) and framework materials (e. g., Prussian blue analogs). This perspective seeks to illustrate the structural origin, theoretical foundation, and experimental evidences of surface-like diffusion. Unlike classical lattice diffusion, which typically involves ionic hopping between adjacent interstitial sites in solids, surface-like diffusion occurs when ions-that are significantly smaller than the interstitials-migrate along the off-center path in the diffusion channel. This mechanism results in an exceptionally low activation energy (Ea) down to 0.2 eV, which is crucial for achieving high-rate performance in electrochemical devices such as lithium-ion and sodium-ion batteries. This concept review also discusses the criteria to identify materials with potential surface-like diffusion and outlines theoretical and experimental tools to capture such phenomenon. Several candidates for further investigation are proposed based on the current understanding of the mechanism.

Nanostructure-Integrated Electrode Based on Ni/NiO Coaxial Bilayer Nanotube Array with Large Specific Capacitance for Miniaturized Applications

The fast development of portable electronics demands electrodes for supercapacitors that are compatible with miniaturized device applications. In this study, an orderly aligned coaxial bilayer nanotube array made of transition metal/transition metal oxides was adopted as a nanostructure-integrated electrode for applications as miniaturized micro-supercapacitors. Using Ni and NiO as our model materials, the corresponding Ni/NiO-CBNTA electrodes were fabricated using templated growth and post-thermal oxidation. The Ni shells served as parts of the 3D nano-architectured collector, providing a large specific surface area, and the pseudocapacitive NiO layers were directly attached and electrically connected to the collector without any additives. The vertical growth of orderly aligned Ni/NiO-CBNTAs successfully avoided the underutilization of capacitive nanomaterials and allowed the electrolyte to be fully accessed, which manifested full charge storage capabilities under the miniaturizing. It was demonstrated that Ni/NiO-CBNTAs can serve as miniaturized electrodes with an improved specific capacitance of 1125 F/g ≅ 3 A/g, which is comparable to that obtained in a massive load electrode prepared by the conventional slurry-coating technique.

HOF-Enabled Synthesis of Porous PEDOT as an Improved Electrode Material for Supercapacitor

Controlling the nanostructure of conducting polymers (CPs) is essential for enhancing their performance in energy storage applications. Existing CPs often suffer from low effective pseudocapacitance due to poor ion permeability. In this study, we introduce a novel approach using hydrogen-bonded organic frameworks (HOFs) to synthesize porous poly(3,4-ethylenedioxythiophene) (PEDOT). We incorporated 3,4-ethylenedioxythiophene (EDOT) into HOF-16 by leveraging the flexible hydrogen-bonding interactions. Following the polymerization of EDOT, the HOF-16 was removed to form a porous interconnected network of PEDOT. Electrochemical evaluations demonstrated that the porous PEDOT exhibited significantly enhanced performance, including high specific capacitance, excellent rate capability, and ∼95% capacitance retention after 10,000 cycles. Compared to PEDOT prepared without HOF, the porous PEDOT showed a 34% increase in specific capacitance and a 10% improvement in 10,000-cycle capacitance retention. This work highlights the potential of HOF-enabled synthesis in creating high performance conducting polymers, offering a new avenue to improve supercapacitor performance, particularly in capacitance and cycling stability.

The Role of Alkali Metal Ions in Cooperative Electrocatalysis by Bifunctional Co-Mn-Mixed Phosphates

Developing cost-effective, non-precious metal bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for advancing sustainable energy storage and conversion technologies, including zinc-air batteries, fuel cells, and water electrolyzers. This study presents a one-pot synthesis of cobalt-manganese mixed phosphates as effective bifunctional electrocatalysts for both ORR and OER. Among the catalysts tested, Na-Co-Mn-P [NaCo1.5Mn1.5(HPO4)2(PO4)] exhibited the highest catalytic activity, with a minimal ΔE of 0.86 V, indicating superior performance. The incorporation of alkali metals and the synergistic effects of metal and phosphate components enhance conductivity, electrochemical surface area, and mixed valency of transition metals, contributing to improved electrocatalytic activity. This work highlights a straightforward synthesis method and the beneficial role of metal-phosphate synergy in oxygen electrocatalysis.

Zinc ferrite nanoparticles as electrode material for supercapacitors

In the realm of sustainable and renewable nanotechnology, supercapacitors have appeared as the dominant solution for energy conversion and storage. Ferrites have been widely explored in magnetic, electronic and microwave devices, and are now being explored for applications in energy storage devices due to the possibility of achieving fast and reversible surface Faradic reactions. From this perspective, a simple and inexpensive chemical co-precipitation method was used to synthesize ultrasmall ZnFe2O4nanoparticles (NPs). As an electrode material the ZnFe2O4NPs show a gravimetric capacitance of 186.6 F g-1at a current density of 1 A g-1in 1 M H2SO4. Furthermore, the ZnFe2O4NP-based electrode shows exceptional capacitive retention of 98% over 1000 cycles at a current density of 3 A g-1. An asymmetric ZnFe2O4NP//NiO NP device was fabricated, which achieved a power density of 302.3 W kg-1at a current density of 1.5 A g-1and an energy density of 14.85 W h kg-1. After 1500 cycles, the device demonstrated capacity retention of 99.4% at 1.5 A g-1in long-term stability testing with 100% efficiency. Our study suggests that ZnFe2O4NPs are promising as a material for future energy storage applications.

A cobalt-aluminium layered double hydroxide with a nickel core-shell structure nanocomposite for supercapacitor applications

Layered double hydroxides (LDHs) are promising structures in applications including supercapacitors, which are claimed to help in arresting environmental chaos by their ability in energy storing. In this work, a Co-Al LDH and its metallic Ni core-shell nanocomposite were prepared and described using Fourier transform infrared (FTIR), X-ray diffractometer (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The two materials were electrochemically examined. The specific capacitance in current density of 1 A g-1 was 90 C g-1 (341.75 F g-1) and 210 C g-1 (792.5 F g-1) for the LDH and its composite, respectively. Compared with similar composites, the specific capacitance, especially the composite has a larger value in the order of 1.08-5.82 of magnitude. Moreover, the cycle stability test shows a slow drop at current density 4 A g-1 within 3,000 cycles, meaning that for the pure hydroxide and its Ni composite, a loss of 21% and 10% of specific capacitance was observed, respectively.

Development of the all-solid-state flexible supercapacitor membranes via RAFT-mediated grafting and electrospun nanofiber modification of track-etched membranes

Developing novel membranes marks a significant advancement in flexible energy storage systems. In this work, a hybrid track-etched membrane (TeM) was synthesized through RAFT-mediated polymerization, where poly(acrylic acid) (PAA) was grafted onto both the nanopore walls and surface of PET-based TeMs (PET-g-PAA), creating a stable and functionalized matrix for further enhancements. The membrane was then modified by incorporating electrospun composite nanofibers made from poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) as the polymer matrix, ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EM-IMBF4) as the supporting electrolyte, and graphene oxide (GO) as the ionic conductivity enhancer. The nanofibers (PVDF-HFP_GO) were deposited on either one or both surfaces of the grafted membrane. These modifications substantially improved the membrane's active surface area, porosity, and electrochemical performance, positioning it as a strong candidate for flexible energy storage applications. Comprehensive characterizations verified the successful modification and enhanced properties, including FTIR, SEM-EDX, XPS, TGA, porosity analysis, and contact angle measurements. Electrochemical performance was evaluated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Among the tested membranes, the one modified with 0.5% GO-containing nanofibers demonstrated the highest capacitance and coulombic efficiency. Although the membrane showed strong charge/discharge efficiency and high initial performance, performance degradation was observed after extended cycling, particularly at higher current densities. The ionic conductivity of the hybrid membranes (with a GO concentration of 0.5%) reaches 14.83 × 10-3 mS cm-1 for single-sided nanofiber-covered membranes and 39.08 × 10-3 mS cm-1 for double-sided nanofiber-covered membranes, while for similar samples without addition of GO this values were found to be of 1.42 × 10-3 mS cm-1, which is significantly higher than conventional polymer-based electrolyte membranes (∼10-4 to 10-2 mS cm-1), and comparable to advanced ionic gel-based systems (∼10-2 to 10-1 mS cm-1). The synergistic effects of PAA grafting and PVDF-HFP_GO fibers delivered competitive charge/discharge efficiency when compared to similar systems, though further optimization of current density and cycling stability is required. This study highlights the potential of combining the RAFT-mediated grafting technique with electrospun composite nanofibers in modifying TeMs to develop durable and flexible supercapacitor membranes with promising electrochemical performance.

A low-temperature-tolerant and non-flammable cellulose/HEC/PVA eutectogel for flexible asymmetric supercapacitors

Asymmetric supercapacitors (ASCs), which combine the advantages of electric double-layer capacitors and pseudocapacitors, have attracted more and more research interest. However, the performance of water-based ASCs often faces the challenge of electrolyte freezing at low temperatures. To resolve the problem, a ternary deep eutectic solvent (DES) with an eutectic point of less than -100 °C was first prepared. After the DES was integrated into a polymer matrix composed of microcrystalline cellulose (MCC), hydroxyethyl cellulose (HEC), and poly(vinyl alcohol) (PVA), a flexible and non-flammable eutectogel was fabricated. The optimized eutectogel not only exhibited an ionic conductivity of 23.4 mS cm-1 even at -20 °C, but also displayed a tensile strength value of about 0.37 MPa and an elongation value at break of nearly 600 %. The ASC with a eutectogel demonstrated a high voltage window of 0-1.8 V, an energy density of 15.13 Wh kg-1 at a power density of 87.52 W kg-1, and fantabulous cycling stability with ∼90 % capacitance retention after 5000 cycles. The flexible ASC with such a eutectogel could work well in a wide temperature range from -20 to 60 °C. It is expected that this work could present valuable insights for the development of wide-temperature gel polymer electrolytes in ASC applications.

Structure and Morphological Properties of Cobalt-Oxide-Based (Co3O4) Materials as Electrodes for Supercapacitors: A Brief Review

Over the past 15 years, there has been a significant increase in the search for environmentally friendly energy sources, and transition-metal-based energy storage devices are leading the way in these new technologies. Supercapacitors are attractive in this regard due to their superior energy storage capabilities. Electrode materials, which are crucial components of supercapacitors, such as cobalt-oxide-based electrodes, have great qualities for achieving high supercapacitor performance. This brief review presents some basic concepts and recent findings on cobalt-based materials used to fabricate electrodes for supercapacitors. The text also clarifies how morphological characteristics typically influence certain properties. The inner surface of the electrode exhibits several properties that change to provide it a great boost in specific capacitance and charge storage. Porous structures with defined pore sizes and shapes and high surface areas are important features for improving electrochemical properties. Finally, we present some perspectives for the development of cobalt-oxide-based supercapacitors, focusing on their structure and properties.

Rate capability and electrolyte concentration: Tuning MnO2 supercapacitor electrodes through electrodeposition parameters

Manganese dioxide (MnO2) is a well-known pseudocapacitive material that has been extensively studied and highly regarded, especially in supercapacitors, due to its remarkable surface redox behavior, leading to a high specific capacitance. However, its full potential is impeded by inherent characteristics such as its low electrical conductivity, dense morphology, and hindered ionic diffusion, resulting in limited rate capability in supercapacitors. Addressing this issue often requires complicated strategies and procedures, such as designing sophisticated composite architectures. This study introduces a straightforward and cost-effective approach to tune and enhance the rate capability of MnO2 pseudocapacitor electrodes fabricated via the electrodeposition method. Among the electrodeposition parameters, the deposition time and electrolyte concentration, which influence the mass loading, electrode thickness, microstructure, and electrochemical properties, were the primary focus. Various electrodes were prepared potentiostatically in a two-electrode cathodic electrodeposition setup on a Ni foam substrate in a KMnO4 aqueous electrolyte, with bath concentrations (in terms of Mn ion) of 0.01 and 0.1 M, and electrodeposition times ranging from 1 to 15 min. Optimal rate capabilities were achieved at low bath concentrations and deposition times, primarily due to the structural properties of electrodes prepared under such circumstances. While electrodeposition at a 0.1 M electrolyte concentration resulted in the formation of electrolytic MnO2 with high supercapacitive rate sensitivity, reducing the bath concentration to 0.01 M primarily led to the formation of birnessite δ-MnO2, capable of maintaining a reasonable specific capacitance in the range of approximately 90-100 Fg-1 with almost no sensitivity to the charging/discharging rate, as confirmed by galvanostatic charge-discharge (1-10 Ag-1) and cyclic voltammetry (10-100 mVs-1) examinations. Along with the positive structural impacts of the layered birnessite with large interlayer spacing, the porous morphology (vertically aligned two-dimensional interconnected columns) and low thickness (≈2 μm) of the electrode prepared at the lowest bath concentration and electrodeposition time (0.01 M in 1 min electrode) contributed to its fast ionic diffusion kinetics for pseudocapacitive charge storage and the consequent high rate capability.

Sterically Induced Enhancement in the Electrochemical Stability of Salen-Type Cathode Materials

This study investigates the electrochemical degradation mechanisms of nickel-salen (NiSalen) polymers, with a focus on improving the material's stability in supercapacitor applications. We analyzed the effects of steric hindrance near the nickel center by incorporating different bulky substituents into NiSalen complexes, aiming to mitigate water-induced degradation. Electrochemical performance was assessed using cyclic voltammetry, operando conductance, and impedance measurements, while X-ray photoelectron spectroscopy (XPS) provided insights into molecular degradation pathways. The results revealed that increased steric hindrance from methyl groups significantly reduced the degradation rate, particularly in water-containing electrolytes, by hindering water coordination to the Ni center. Among the studied polymers, the highly substituted poly[Ni(Saltmen)] exhibited superior stability with minimal capacity loss. Density functional theory (DFT) calculations further supported that steric protection around the Ni atom effectively lowers the probability of water coordination. These findings suggest that sterically enhanced NiSalen polymers may offer a promising path toward durable supercapacitor electrodes, highlighting the route of molecular engineering to enhance material stability.

Deposition of VS2/MoS2bilayer layers of 2D material on nickel inverse opal structural substrates by SILAR and ECD processes as supercapacitor electrodes

The composition, microstructure, and electrochemical properties of the two kinds of thin film electrode materials, namely VS2/MoS2/Ni-IOS and VS2/MoS2/Ni-foam, were analyzed. The research results indicate that the self-assembled photonic crystal (PhC) templates with adjusted electrophoretic self-assembly processing parameters (100 V cm-1; 7 min) would lead the specimen to a face-centered closely packed structure. Metallic nickel inverse opal structure (IOS) PhCs whose thickness can be freely regulated simply by electrochemical deposition time. VS2and MoS2are 2D materials with excellent electrochemical properties. We employed them as the electroactive material in this study and deposited them onto nickel IOS (Ni-IOS) surfaces to form a composite of The specimens exhibited an excellent specific capacitance (2180 F g-1) at a charge-discharge current density of 5 A g-1. After the 2000 cycles during the life test, the sample can still retain the original specific capacitance value by 72.3%. The IOS PhC substrate produced in this work is designed as VS2/MoS2/Ni-IOS supercapacitor electrode materials, which is proved to offer a significant technical contribution to the application of 2D materials in high-performance supercapacitors currently.

Electrospun Mesoporous Ni0.5Zn0.5Fe2O4 - CNT - Hollow Carbon Ternary Composite Nanofibers as High Performance Electrodes for Advanced Symmetric Supercapacitors

Spinel ferrites have attracted considerable interest in energy storage systems due to their unique magnetic, electrical and catalytic properties. However, they suffer from poor electronic conductivity and low specific capacity. We have addressed this limitation by synthesizing composite hollow carbon nanofibers (HCNF) embedded with nanostructured Nickel Zinc Ferrite (NZF) and Multiwalled carbon nanotubes (CNT), through coaxial electrospinning. These ternary composite nanofibers NZF-CNT-HCNF have a high specific capacity of 833 C g-1 at a current density of 1 A g-1 and have a capacity retention of 90 % after 3000 cycles. Their performance is much better than pure NZF fibers (180 C g-1) or hollow carbon nanofibers (96 C g-1), suggesting synergy between various constituents of the composite. A symmetric supercapacitor fabricated from NZF-CNT-HCNF composite nanofibers (30 % NZF) has a high specific capacity of 302 C g-1 (302 A g-1) at a current density of 1 A g-1 and has a capacity retention of 95 % after 5000 cycles. At the same current density, the device has a high energy density of 39 Whkg-1 and power density of 1000 Wkg-1 at a current density of 1 A g-1. This performance can be attributed to the high specific surface area (776 m2 g-1), mesoporosity (pore size ~4 nm), interconnectedness of the nanofibers and high electrical conductivity of CNTs. These fibers can be used as light-weight high performance electrode materials in advanced energy storage devices.

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.

Facile Synthesis of Mesoporous NiCo2O4 Nanosheets on Carbon Fibers Cloth as Advanced Electrodes for Asymmetric Supercapacitors

The NiCo2O4 Nanosheets@Carbon fibers composites have been successfully synthesized by a facile co-electrodeposition process. The mesoporous NiCo2O4 nanosheets aligned vertically on the surface of carbon fibers and crosslinked with each other, producing loosely porous nanostructures. These hybrid composite electrodes exhibit high specific capacitance in a three-electrode cell. The asymmetric supercapacitor (NiCo2O4 Nanosheets@Carbon fibers//Graphene oxide) displayed a high specific capacitance of 91 F g-1 and excellent cycling stability with a capacitance retention of 94.5% at 5 A g-1 after 10,000 cycles. The device also achieved a notable energy density of 52 Wh kg-1 coupled with a power density of 3.5 kW kg-1 and a high power density of 7.1 kW kg-1 with an energy density of 21 Wh kg-1. This study shed light on the great potential of this asymmetric device as future supercapacitor.

Carbon Nanofibers as Supporting Substrate for Growth of Polyaniline Nanorods on Fe2O3 Nanoneedles toward Electrochemical Energy Storage

Iron-oxide (Fe2O3) nanoneedles were first in situ grown on the surface of carbon nanofibers (CNFs) using hydrothermal and N2 annealing process, and then polyaniline (PANI) was coated on the Fe2O3 nanoneedles to form network-like nanorods through dilute solution polymerization. The PANI/Fe2O3/CNFs binder-free electrode exhibited a high specific capacitance of 603 F/g at 1 A/g with good rate capability. (The capacitance loss was about 48.3% when the current density increased from 1.0 to 5.0 A/g.) It was caused by the fact that the PANI/Fe2O3/CNFs with a well-connected structure could provide a continuous electron transport path and improve the conductivity of the entire electrode. The solid-state hybrid PANI/Fe2O3/CNFs∥PANI/Fe2O3/CNFs symmetric device also achieved a high energy density of 29.85 Wh/kg at a power density of 500 W/kg. This universal compatible synthetic method for the PANI/Fe2O3/CNFs electrode could extend to other supercapacitor electrode systems, making it easy to fabricate various ternary electrodes for supercapacitors.

Functionalised biphenylene and graphenylene: excellent choices for supercapacitor electrodes

Quantum capacitance (CQ) is a crucial parameter that reflects the energy storage capacity of supercapacitors. In this work, we extensively investigate the effect of vacancy induced defects on quantum capacitance of well studied biphenylene (BPN) and graphenylene (GPN) monolayers. Based on density functional theory (DFT), we have systematically studied the consequence of vacancies on structural stability, charge distribution, electronic band structure of pristine systems, and correlated this with the variation of quantum capacitance with applied voltage. The results demonstrate that insertion of a vacancy significantly improves the density of states (DOS) profile around the Fermi level for both structures, attributed to the localisation of charge carriers. This leads to higher CQ values for relatively lower potential, with the highest value of CQ being 221 μF cm-2 for defective BPN. Furthermore, we have calculated the density of surface charge for different voltages to evaluate the adaptability of particular materials as a cathode or anode. It is found that both pristine and defective BPN are more preferable as anode materials. It is noteworthy that GPN and its vacancy induced structure, stand-out as superior candidates for a symmetric supercapacitor in aqueous systems. This work will provide valuable insights to design BPN and GPN-based high performance electrode materials for electric double layer (EDL) supercapacitors.

Fundamentals and Implication of Point of Zero Charge (PZC) Determination for Activated Carbons in Aqueous Electrolytes

The point of zero charge (PZC) is a crucial parameter for investigating the charge storage mechanisms in energy storage systems at the molecular level. This paper presents findings from three different electrochemical techniques, compared for the first time: cyclic voltammetry (CV), staircase potentio electrochemical impedance spectroscopy (SPEIS), and step potential electrochemical spectroscopy (SPECS), for two activated carbons (ACs) with 0.1 mol L-1 aqueous solution of LiNO3, Li2SO4, and KI. The charging process of AC operating in aqueous electrolytes appears as a complex phenomenon - all ionic species take an active part in electric double-layer formation and the ion-mixing zone covers a wide potential region. Therefore, the so-called PZC should not be considered as an absolute one-point potential value, but rather as a range of zero charge (RZC). SPECS technique is found to be a universal and fast method for determining RZC, as applied here together with the EQCM. In most cases, the RZC covers a potential range from ≈100 to ≈200 mV and the correlation of the range with the carbon microtexture is clear, highlighting the role of the ion-sieving effect. It is postulated that PZC for porous materials in aqueous electrolytic solutions should be considered instead as RZC.

A simple method of fabrication hybrid electrodes for supercapacitors

The increasing need for electrode materials exhibiting improved performance to meet the requirements of supercapacitors is on the rise. Hybrid electrodes, which combine reduced graphene oxide (rGO) with transition metal-based oxides, have emerged as promising materials due to their impressive specific capacitance and cost-effectiveness, attributed to their synergistic properties. In the present study, a binder-free CoOrGO composite electrode was synthesized using a facile, fast, and simple one-step co-precipitation method. This was done to improve both capacity and stability for supercapacitor applications. The composite materials underwent comprehensive characterization utilizing various surface analytical techniques, including X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FE-SEM), fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. Electrochemical measurements of the CoOrGO composite revealed at current density of 2 A cm- 2 a specific capacitance of 132.3 mF cm- 2, with an impressive 95.91% retention of capacitance after 7000 cycles. The results from electrochemical impedance spectroscopy (EIS) highlighted a meager low relaxation time constant of 0.53 s for the composite films. The reason behind this can be linked to the synergistic interactions, and minimal charge transfer resistance exhibited by the porous electrode without binders. Based on the obtained results, this work introduces a flexible methodology for crafting advanced energy storage systems. This demonstrates the potential for designing high-efficiency supercapacitors that are suitable for a broad range of large-scale applications.

Exploring the electrochemical properties and lithium insertion mechanisms in akaganeite (β-FeOOH) - a combined DFT/experimental study

Akaganeite (β-FeOOH) has been intensely investigated to be used in different electrochemical applications as a cathode material in Li-ion batteries owing to its unique structural characteristics, including channels capable of accommodating and reversibly extracting charged species such as lithium or sodium ions. We revisited the synthesis, and its electrochemical properties based on a combined experimental/theoretical approach aiming to understand the mechanism of the electron transfer in this material. Electrochemical investigations, employing Li2SO4 aqueous electrolyte, unveiled notable alterations in the charge/discharge profiles. The initial discharge curve revealed distinct plateaus at 3.4 V and 2.9 V, with the absence of the former in subsequent cycles, indicating irreversible reactions in the initial cycle. Furthermore, density functional theory (DFT) calculations were employed to elucidate the impact of lithium atom insertion on the electronic and structural properties of akaganeite. We gained insights into the underlying electrochemical processes calculating band structures, density of states, and topological analysis based on Bader's theory. The calculated oxidation potentials (3.2 V) closely matched experimental observations, attributing the 3.2 V plateau to lithium insertion into the akaganeite structure.

A Two-Step Synthesis of Porous Nitrogen-Doped Graphene for Electrochemical Capacitors

Porous nitrogen-doped graphene (PNG) materials with high conductivity, high surface area, and chemical stability have displayed superior performance in electrochemical capacitors. However, previously reported methods for fabricating PNG render the processes expensive, hard to control, limited in production, and unsafe as well, thus largely restricting their practical applications. Herein, we present a facile two-step calcination method to prepare PNG using petroleum asphalt as the carbon source to provide the original three-dimensional porous structure directly and using environmentally friendly and high nitrogen content urea as the nitrogen source without adding any etching agent. The porous structure in PNG can largely increase its specific surface area, and the introduction of nitrogen atoms can effectively increase the degree of defects and improve the wettability of PNG. As a result, PNG displays a high specific capacitance of 157 F g-1 at a current density of 1 A g-1 and cycling stability while maintaining 98.68% initial capacitance after 10,000 cycles.

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

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

Chitosan-derived carbon and NiCo2O4 aerogel composite for high-performance supercapacitors

This work presents a multi-step strategy to fabricate chitosan-derived nitrogen-doped carbon (CCS) and CCS/NiCo2O4 (CNCO) aerogels for supercapacitor application. The various mass fractions of NiCo precursors and chitosan as well as different carbonization temperatures, were investigated. The best rationally designed aerogel carbonized at 300 °C (CNCO-2) had the highest specific surface area and nitrogen content. It exhibited a high capacitance of 1200 F g-1 at 1.0 A g-1 as an active electrode material for supercapacitors. In addition, the fully solid-state CCS//CNCO-2 device had a high capacitance of 172 F g-1 at 1.0 A g-1 and excellent cyclic stability (over 87 % capacitance retention after 10,000 cycles). This device displayed a maximum energy density of 53 Wh kg-1 at 750 W kg-1. Furthermore, two devices connected in series and parallel indicate typical voltage and capacitance expansion, highlighting practicable applications of chitosan-derived aerogel composites to meet different requirements in energy storage.

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.

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.