M4X3 MXenes: Application in Energy Storage Devices.

MXene has garnered widespread recognition in the scientific community due to its remarkable properties, including excellent thermal stability, high conductivity, good hydrophilicity and dispersibility, easy processability, tunable surface properties, and admirable flexibility. MXenes have been categorized into different families based on the number of M and X layers in Mn+1Xn, such as M2X, M3X2, M4X3, and, recently, M5X4. Among these families, M2X and M3X2, particularly Ti3C2, have been greatly explored while limited studies have been given to M5X4 MXene synthesis. Meanwhile, studies on the M4X3 MXene family have developed recently, hence, demanding a compilation of evaluated studies. Herein, this review provides a systematic overview of the latest advancements in M4X3 MXenes, focusing on their properties and applications in energy storage devices. The objective of this review is to provide guidance to researchers on fostering M4X3 MXene-based nanomaterials, not only for energy storage devices but also for broader applications.

Hexagon MXene based heterojunction interface with high ion adsorption and electron transfer efficiency for soft-package potassium-ions aqueous supercapacitors.

Potassium-ion hybrid capacitors (PIHC) are considered as ideal large-scale rechargeable energy storage devices due to their low-cost, high-power density and environmental protection. However, a low energy density is the main factor restricting the practical application of PIHC. The interface is formed on the surface of electrode material of PIHC through strong correlation to construct heterojunction, which can significantly improve the performance of ion energy storage. However, how to reveal the influence of the interfacial state of the heterojunction on the adsorption and electron transmission of energy storage ions at the atomic level is still one of the key scientific problems in this field. In this work, metal ion intercalation and microwave-assisted in-situ etching are used to construct the Hexagon MXene Ti3C2 heterojunction with TiOHO strong correlation. At the interface of heterojunction, TiOHO highway for electron transmission is developed to improve the rate performance of PIHC. Through experimental and theoretical calculation, the optimum adsorption position and maximum adsorption amount of potassium-ion at the single interface of heterojunction are obtained, and the specific energy density of PIHC is increased. This lays a foundation for the practical application of high-performance soft-package PIHC.

Biodegradable MoNx@Mo-foil electrodes for human-friendly supercapacitors.

With the advancement in the field of biomedical research, there is a growing demand for biodegradable electronic devices. Biodegradable supercapacitors (SCs) have emerged as an ideal solution for mitigating the risks associated with secondary surgeries, reducing patient discomfort, and promoting environmental sustainability. In this study, MoNx@Mo-foil was prepared as an active material for biodegradable supercapacitors through high-temperature and nitridation processes. The composite electrode exhibited superior electrochemical performance in both aqueous and solid-state electrolytes. In the case of the solid-state electrolyte, the MoNx@Mo-foil composite electrode-based device demonstrated excellent cycling stability and electrochemical performance. Additionally, the composite electrode exhibited rapid and complete biodegradability in a 3% H2O2 solution. Through detailed experimental analysis and performance testing, we verified the potential application of the MoNx@Mo-foil composite electrode in biodegradable supercapacitors. This work provides a new choice of degradable material for developing biomedical electronic devices.

V-MXenes for Energy Storage/Conversion Applications.

MXenes, a two-dimensional (2D) material, exhibit excellent optical, electrical, chemical, mechanical, and electrochemical properties. Titanium-based MXene (Ti-MXene) has been extensively studied and serves as the foundation for 2D MXenes. However, other transition metals possess the potential to offer excellent properties in various applications. This comprehensive review aims to provide an overview of the properties, challenges, key findings, and applications of less-explored vanadium-based MXenes (V-MXenes) and their composites. The current trends in V-MXene and their composites for energy storage and conversion applications have been thoroughly summarized. Overall, this review offers valuable insights, identifies potential opportunities, and provides key suggestions for future advancements in the MXenes and energy storage/conversion applications.

Improved Electrochemical Performance of Aqueous Hybrid Supercapacitors Using CrCo2O4 Mesoporous Nanowires: An Innovative Strategy toward Sustainable Energy Devices.

High-rate aqueous hybrid supercapacitors (AHSCs) have attracted relevant scientific significance owing to their expected energy density, supercapacitor-level power density, and battery-level energy density. In this work, a bimetallic nanostructured material with chromium-incorporated cobalt oxide (CCO, i.e., CoCr2O4) was prepared via a hydrothermal method to form a stable cubic obelisk structure. Compared with CCO materials prepared using traditional methods, CCO displayed a nanowire structure (50 nm diameter), suggesting an enhanced specific surface area and a large number of active sites for chemical reactions. The electrode possessed a high specific capacitance (2951 F g-1) at a current density of 1 A g-1, minimum Rct (0.135 Ω), and the highest capacitance retention (98.7%), making it an ideal electrode material for AHSCs. Ex situ analysis based on X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed a favorable stability of CCO after 10,000 cycles without any phase changes being detected. GGA and GGA + U methods employed in density functional theory (DFT) also highlighted the enhanced metallic properties of CCO originating from the synergistic effect of semiconducting Cr2O3 and Co3O4 materials.

Mo-based MXenes: Synthesis, properties, and applications.

Ti-MXene allows a range of possibilities to tune their compositional stoichiometry due to their electronic and electrochemical properties. Other than conventionally explored Ti-MXene, there have been ample opportunities for the non-Ti-based MXenes, especially the emerging Mo-based MXenes. Mo-MXenes are established to be remarkable with optoelectronic and electrochemical properties, tuned energy, catalysis, and sensing applications. In this timely review, we systematically discuss the various organized synthesis procedures, associated experimental tunning parameters, physiochemical properties, structural evaluation, stability challenges, key findings, and a wide range of applications of emerging Mo-MXene over Ti-MXenes. We also critically examined the precise control of Mo-MXenes to cater to advanced applications by comprehensively evaluating the summary of recent studies using artificial intelligence and machine learning tools. The critical future perspectives, significant challenges, and possible outlooks for successfully developing and using Mo-MXenes for various practical applications are highlighted.

Design and Advanced Manufacturing of NU-1000 Metal-Organic Frameworks with Future Perspectives for Environmental and Renewable Energy Applications.

Metal-organic frameworks (MOFs) represent a relatively new family of materials that attract lots of attention thanks to their unique features such as hierarchical porosity, active metal centers, versatility of linkers/metal nodes, and large surface area. Among the extended list of MOFs, Zr-based-MOFs demonstrate comparably superior chemical and thermal stabilities, making them ideal candidates for energy and environmental applications. As a Zr-MOF, NU-1000 is first synthesized at Northwestern University. A comprehensive review of various approaches to the synthesis of NU-1000 MOFs for obtaining unique surface properties (e.g., diverse surface morphologies, large surface area, and particular pore size distribution) and their applications in the catalysis (electro-, and photo-catalysis), CO2 reduction, batteries, hydrogen storage, gas storage/separation, and other environmental fields are presented. The review further outlines the current challenges in the development of NU-1000 MOFs and their derivatives in practical applications, revealing areas for future investigation.

Recent trends in wastewater treatment by using metal-organic frameworks (MOFs) and their composites: A critical view-point.

Respecting the basic need of clean and safe water on earth for every individual, it is necessary to take auspicious steps for waste-water treatment. Recently, metal-organic frameworks (MOFs) are considered as promising material because of their intrinsic features including the porosity and high surface area. Further, structural tunability of MOFs by following the principles of reticular chemistry, the MOFs can be functionalized for the high adsorption performance as well as adsorptive removal of target materials. However, there are still some major concerns associated with MOFs limiting their commercialization as promising adsorbents for waste-water treatment. The cost, toxicity and regenerability are the major issues to be addressed for MOFs to get insightful results. In this article, we have concise the current strategies to enhance the adsorption capacity of MOFs during the water-treatment for the removal of toxic dyes, pharmaceuticals, and heavy metals. Further, we have also discussed the role of metallic nodes, linkers and associated functional groups for effective removal of toxic water pollutants. In addition to conformist overview, we have critically analyzed the MOFs as adsorbents in terms of toxicity, cost and regenerability. These factors are utmost important to address before commercialization of MOFs as adsorbents for water-treatment. Finally, some future perspectives are discussed to give directions for potential research.

2D MXenes Nanosheets for Advanced Energy Conversion and Storage Devices: Recent Advances and Future Prospects.

Since the initial MXenes were discovered in 2011, several MXene compositions constructed using combinations of various transition metals have been developed. MXenes are ideal candidates for different applications in energy conversion and storage, because of their unique and interesting characteristics, which included good electrical conductivity, hydrophilicity, and simplicity of large-scale synthesis. Herein, we study the current developments in two-dimensional (2D) MXene nanosheets for energy storage and conversion technologies. First, we discuss the introduction to energy storage and conversion devices. Later, we emphasized on 2D MXenes and some specific properties of MXenes. Subsequently, research advances in MXene-based electrode materials for energy storage such as supercapacitors and rechargeable batteries is summarized. We provide the relevant energy storage processes, common challenges, and potential approaches to an acceptable solution for 2D MXene-based energy storage. In addition, recent advances for MXenes used in energy conversion devices like solar cells, fuel cells and catalysis is also summarized. Finally, the future prospective of growing MXene-based energy conversion and storage are highlighted.

In-situ construction of binder-free MnO2/MnSe heterostructure membrane for high-performance energy storage in pseudocapacitors.

Manganese (Mn)-based oxides are considered suitable positive electrode materials for supercapacitors (SCs). However, their cycle stability and specific capacitance are significantly hindered by key restrictions such as structural instability and low conductivity. Herein, we demonstrated a novel nanorod (NR)-shaped heterostructured manganese dioxide/manganese selenide membrane (MnO2/MnSe) on carbon cloth (CC) (denoted as MnO2/MnSe-NR@CC) with a high aspect ratio by a straightforward and facile hydrothermal process. Experiments have demonstrated that doping selenium atoms to oxygen sites reduce electronegativity, increasing the intrinsic electronic conductivity of MnO2, decreasing electrostatic interactions with electrolyte ions, and thus boosting the reaction kinetics. Further, the selenium doping results in an amorphous surface with extensive oxygen defects, which contributed to the emergence of additional charge storage sites with pseudocapacitive characteristics. As expected, novel heterostructured MnO2/MnSe-NR@CC as an electrode for SC exhibits a high capacitance of 740.63 F/g at a current density of 1.5 A/g, with excellent cycling performance (93% capacitance retention after 5000 cycles). The MnO2/MnSe-NR@CC exhibited outstanding charge storage capability, dominating capacitive charge storage (84.6% capacitive at 6 mV/s). To examine the practical applications of MnO2/MnSe-NR@CC-ASC as a positive electrode, MnO2/MnSe-NR@CC//AC device was fabricated. The MnO2/MnSe-NR@CC//AC-ASC device performed exceptionally well, with a maximum capacitance of 166.66 F/g at 2 A/g, with a capacitance retention of 94%, after 500 GCD cycles. Additionally, it delivers an energy density of 75.06 Wh/kg at a power density of 1805.1 W/kg and maintains 55.044 Wh/kg at a maximum power density of 18,159 W/kg. This research sheds fresh information on the anionic doping method and has the potential to be applied to the synthesis of positive electrode materials for energy storage applications.

Green synthesized Ag decorated CeO2 nanoparticles: Efficient photocatalysts and potential antibacterial agents.

Implication of natural resources for manufacturing of nanoparticles is sustainable, economical and contaminant free approach towards ecological and medical applications. Herein, CeO2 and Ag/CeO2 nanoparticles are green synthesized from Morinda tinctoria plant extract. The phase structure, surface morphology, optical identity, Ce(III) and Ce(IV) valency of the synthesized CeO2 and Ag/CeO2 nanoparticles are explored. The X-ray diffraction analysis indicated the formation of cubic phase CeO2 and cubic silver decorated CeO2 nanoparticles. Fourier transform infrared (FTIR) spectroscopy revealed the metal decoration of CeO2 nanoparticles, metal-oxygen stretching, indicating the plant molecules reduction and stabilization. UV-visible spectroscopy shown the decreased band gap owing to silver modification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs displayed spherical morphology of the nanoparticles. Elemental composition and sample purity is assessed by energy dispersive spectroscopy (EDS). Double oxidation of Ce, double splitting energy of Ag and lattice oxygen are observed from X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of Ag/CeO2 exposed the enhanced photocatalytic activity up to 94% where CeO2 nanoparticles gave 60% degradation of bromophenol blue (BB). The plasmonic decoration of silver on the ceria surface induced the charge separations and free radical reactions. Moreover, Ag/CeO2 nanoparticles are seen as superior antibacterial agents than CeO2 towards both E.coli and S.aureus. Hence, the silver decorated metal oxide photocatalyst successfully degraded the BB dye and inactivated the bacterial strains. This report established a future research in green synthesis of multipurpose metal nanoparticles.

A New MBH Adduct as an Efficient Ligand in the Synthesis of Metallodrugs: Characterization, Geometrical Optimization, XRD, Biological Activities, and Molecular Docking Studies.

This article reports the synthesis, characterization, geometrical optimization, and biological studies of new MBH-based organometallic compounds of medicinal significance. The ligand (MNHA) was prepared via the Morita-Baylis-Hillman (MBH) synthetic route, from aromatic aldehyde containing multiple functional groups. Metal complexes were prepared in an alkaline medium and under other suitable reaction conditions. Spectral and elemental analyses were used to identify the structural and molecular formulas of each compound. Optimized geometry was determined through density functional theory (DFT) B3LYP and 6-311++ G (d,p) basis set for the MBH adduct, whereas structures of novel complexes were optimized with the semi-empirical PM6 method. Powder XRD analysis furnished the crystal class of complexes, with Co3+, Cr3+, and Mn2+ being cubic, while Ni2+ was hexagonal, and Cu2+ was orthorhombic. Moreover, the ligand, along with Ni2+ and Co3+ complexes, showed profound antibacterial action against S. aureus, E. coli, B. pumilis, and S. typhi. Additionally, all of the complexes were shown to persist in the positive antioxidant potential of the ligand. Contrarily, not a single metal complex conserved the antifungal potentials of the ligand.

Development of Efficient and Recyclable ZnO-CuO/g-C3N4 Nanocomposite for Enhanced Adsorption of Arsenic from Wastewater.

Arsenic (III) is a toxic contaminant in water bodies, especially in drinking water reservoirs, and it is a great challenge to remove it from wastewater. For the successful extraction of arsenic (III), a nanocomposite material (ZnO-CuO/g-C3N4) has been synthesized by using the solution method. The large surface area and plenty of hydroxyl groups on the nanocomposite surface offer an ideal platform for the adsorption of arsenic (III) from water. Specifically, the reduction process involves a transformation from arsenic (III) to arsenic (V), which is favorable for the attachment to the -OH group. The modified surface and purity of the nanocomposite were characterized by SEM, EDX, XRD, FT-IR, HRTEM, and BET models. Furthermore, the impact of various aspects (temperatures, pH of the medium, the concentration of adsorbing materials) on adsorption capacity has been studied. The prepared sample displays the maximum adsorption capacity of arsenic (III) to be 98% at pH ~ 3 of the medium. Notably, the adsorption mechanism of arsenic species on the surface of ZnO-CuO/g-C3N4 nanocomposite at different pH values was explained by surface complexation and structural variations. Moreover, the recycling experiment and reusability of the adsorbent indicate that a synthesized nanocomposite has much better adsorption efficiency than other adsorbents. It is concluded that the ZnO-CuO/g-C3N4 nanocomposite can be a potential candidate for the enhanced removal of arsenic from water reservoirs.

In Situ Nitrogen Functionalization of 2D-Ti3C2Tx-MXenes for High-Performance Zn-Ion Supercapacitor.

Zinc (Zn) ion supercapacitors (ZISCs) have attracted considerable attention as a viable energy storage technology because they are cost-effective, safe, and environmentally friendly. However, cathode materials with suitable properties are rare and need to be explored. In this regard, metal carbides (MXenes) are a good choice for capacitive energy storage, but they exhibit low capacitance. The energy storage performance of MXenes can be bossed using functionalization with heteroatom doping, e.g., nitrogen (N), to simultaneously modify ZISCs' fundamental characteristics and electrochemical properties. Herein, we present an in-situ N-functionalization of Ti3C2Tx-MXene via a hydrothermal reaction with urea (denoted as N-Ti3C2Tx-MXene). N-functionalization into Ti3C2Tx-MXene raised Ti3C2Tx-MXene's interlayer spacing and boosted the Zn-ion storage in 1 M ZnSO4 electrolyte. The N-Ti3C2Tx-MXene electrode delivered an excellent specific capacitance of 582.96 F/g at 1 A/g and retained an outstanding cycle stability of 94.62% after 5000 cycles at 10 A/g, which is 1.8 times higher than pristine Ti3C2Tx-MXene at identical conditions. Moreover, the N-Ti3C2Tx-MXene//Zn device demonstrated a maximum capacitance of 153.55 F/g at 1 A/g, retained 92% of its initial value after 5000 cycles, and its Coulombic efficiency was ~100%. This strategy considerably reduced Ti3C2Tx-MXene nanosheet restacking and aggregation and enhanced electrochemical performance. Further, this research elucidated N-Ti3C2Tx-MXene's charge-storage process and offered a fresh approach to the rational design of novel electrode materials for ZISCs.

Animal- and Human-Inspired Nanostructures as Supercapacitor Electrode Materials: A Review.

Human civilization has been relentlessly inspired by the nurturing lessons; nature is teaching us. From birds to airplanes and bullet trains, nature gave us a lot of perspective in aiding the progress and development of countless industries, inventions, transportation, and many more. Not only that nature inspired us in such technological advances but also, nature stimulated the advancement of micro- and nanostructures. Nature-inspired nanoarchitectures have been considered a favorable structure in electrode materials for a wide range of applications. It offers various positive attributes, especially in energy storage applications, such as the formation of hierarchical two-dimensional and three-dimensional interconnected networked structures that benefit the electrodes in terms of high surface area, high porosity and rich surface textural features, and eventually, delivering high capacity and outstanding overall material stability. In this review, we comprehensively assessed and compiled the recent advances in various nature-inspired based on animal- and human-inspired nanostructures used for supercapacitors. This comprehensive review will help researchers to accommodate nature-inspired nanostructures in industrializing energy storage and many other applications.

Binder-Free Zinc-Iron Oxide as a High-Performance Negative Electrode Material for Pseudocapacitors.

The interaction between cathode and anode materials is critical for developing a high-performance asymmetric supercapacitor (SC). Significant advances have been made for cathode materials, while the anode is comparatively less explored for SC applications. Herein, we proposed a high-performance binder-free anode material composed of two-dimensional ZnFe2O4 nanoflakes supported on carbon cloth (ZFO-NF@CC). The electrochemical performance of ZFO-NF@CC as an anode material for supercapacitor application was examined in a KOH solution via a three-electrode configuration. The ZFO-NF@CC electrode demonstrated a specific capacitance of 509 F g-1 at 1.5 A g-1 and was retained 94.2% after 10,000 GCD cycles. The ZFO-NF@CC electrode showed exceptional charge storage properties by attaining high pseudocapacitive-type storage. Furthermore, an asymmetric SC device was fabricated using ZFO-NF@CC as an anode and activated carbon on CC (AC@CC) as a cathode with a KOH-based aqueous electrolyte (ZFO-NF@CC||AC@CC). The ZFO-NF@CC||AC@CC yielded a high specific capacitance of 122.2 F g-1 at a current density of 2 A g-1, a high energy density of 55.044 Wh kg-1 at a power density of 1801.44 W kg-1, with a remarkable retention rate of 96.5% even after 4000 cycles was attained. Thus, our results showed that the enhanced electrochemical performance of ZFO-NF@CC used as an anode in high-performance SC applications can open new research directions for replacing carbon-based anode materials.

Investigation on Crystal-Structure, Thermal and Electrical Properties of PVDF Nanocomposites with Cobalt Oxide and Functionalized Multi-Wall-Carbon-Nanotubes.

Nanocomposites of polyvinylidene fluoride (PVDF) with dimensional (1D) cobalt oxide (Co3O4) and f-MWCNTs were prepared successfully by the solution casting method. The impact of 1D Co3O4 filler and 1D Co3O4/f-MWCNTs co-fillers on the structural, thermal, and electrical behavior of PVDF were studied. The crystal structural properties of pure PVDF and its nanocomposite films were studied by XRD, which revealed a significant enhancement of ß-phase PVDF in the resulting nanocomposite films. The increase in ß-phase was further revealed by the FTIR spectroscopic analysis of the samples. TG, DTA, and DSC analyses confirmed an increase in thermal stability of PVDF with the addition of nano-fillers as well as their increasing wt.%. From impedance spectroscopic studies, it was found that the DC conductivity of PVDF increases insignificantly initially (up to 0.1 wt.% of nano-fillers addition), but a significant improvement in DC conductivity was found at higher concentrations of the nano-fillers. Furthermore, it was observed that the DC conductivity decreases with frequency. The increase in DC conductivity corresponded to the strong interactions of nano-fillers with PVDF polymer chains.

Graphene based composite membranes for environmental toxicology remediation, critical approach towards environmental management.

Graphene-based composite membranes, as laminated, stacked, and assembled architectures of graphene, have surpassed other conventional membranes with their advanced and preeminent structural specialization and potential use in a wide range of sustainable and environmental applications. The characteristic membrane features such as distinct laminar morphology, tailored physicochemical properties, as well as extraordinary molecular properties have fascinated scientists. Due to remarkable mechanical properties, these membranes can be easily fabricated. Recent progress has been achieved by graphene and its derivatives-based membranes to purify water and gases for environmental remediation. This review explained the latest and groundbreaking advances in chemical design, fabrication, and application of graphene-based membranes. Special attention is paid to the recent developments on graphene-based composites into membranes with various forms: free-standing, layered, and graphene-based nanocomposite membranes. Furthermore, a unique approach on environmental management with as-fabricated membranes is provided by discussing the effect of physicochemical properties. Consequently, their full-scale use for environmental management, water purification, gas purification, and biological treatments will pave the way for their promising features and realize their future prospects.

Flower-like Highly Open-Structured Binder-Free Zn-Co-Oxide Nanosheet for High-Performance Supercapacitor Electrodes.

Scientific research is being compelled to develop highly efficient and cost-effective energy-storing devices such as supercapacitors (SCs). The practical use of SC devices is hindered by their low energy density and poor rate capability due to the binding agents in fabricating electrodes. Herein, we proposed flower-like highly open-structured binder-free ZnCo2O4 micro-flowers composed of nanosheets supported in nickel foam (ZnCoO@NF) with improved rate capability up to 91.8% when current varied from 2 to 20 A·g-1. The ZnCoO@NF electrode exhibited a superior specific capacitance of 1132 F·g-1 at 2 A·g-1 and revealed 99% cycling stability after 7000 cycles at a high current density of 20 A·g-1. The improved performance of the ZnCoO@NF electrode is attributed to the highly stable structure of the micro/nano-multiscale architecture, which provides both the high conduction of electrons and fast ionic transportation paths simultaneously.

Hydrothermal Synthesis of Binder-Free Metallic NiCo2O4 Nano-Needles Supported on Carbon Cloth as an Advanced Electrode for Supercapacitor Applications.

It is of great significance to design electrochemical energy conversion and storage materials with excellent performance to fulfill the growing energy demand. Bimetallic cobalt/nickel-based electrode materials exhibit excellent electrical conductivity compared to mono oxides. However, their potential as electrode materials for high-performance supercapacitors (SCs) is limited because of their poor cycling stability and high-capacity fading. This work demonstrates the synthesis of binder-free bimetallic NiCo2O4 nano-needles supported on CC (NCO@CC) via a facile and scalable hydrothermal process. Excellent electrical conductivity and interconnected nanostructure of NCO@CC nano-needles provide the fast transfer of electrons with numerous channels for ion diffusion. Owing to such features, the binder-free NCO@CC electrode for SC discloses excellent specific capacitance (1476 Fg-1 at 1.5 Ag-1) with 94.25% capacitance retention even after 5000 cycles. From these outstanding electrochemical performances, it can be inferred that NCO@CC nano-needle array-structured electrodes may be potential candidates for SC applications.