Search Results (77)

Supercapacitors offer high power density, fast charging/discharging capability, and long cycle life, yet their relatively low energy density limits broader deployment in electric vehicles, portable electronics, and grid storage systems. MXenes, a family of two-dimensional transition metal carbides, nitrides, and carbonitrides, have emerged as promising electrode materials due to their high electrical conductivity, tunable surface chemistry, hydrophilicity and intrinsic pseudocapacitive behavior. However, restacking of MXene layers reduces accessible surface area and ion transport efficiency, constraining electrochemical performance. To address this limitation, MXene-based nanocomposites incorporating carbon nanomaterials, conducting polymers, and metal oxides have been extensively developed. This review systematically evaluates recent advances in MXene-based nanocomposites for high-energy-density supercapacitors, highlighting electrochemical performance. A quantitative benchmarking comparison with commonly used electrode materials, including graphene, carbon nanotubes, and activated carbon, is provided. Key challenges in synthesis, performance standardization, and stability are discussed, along with future prospects for developing safer and scalable production methods of MXene-based electrodes. Full article

MXenes have attracted considerable attention as anode materials for sodium-ion batteries (SIBs) because of their metallic conductivity, hydrophilic surfaces, tunable surface terminations, and layered structures. However, pristine MXenes are limited by nanosheet restacking, oxidation instability, heterogeneous surface chemistry, low initial Coulombic efficiency, and insufficient electrode-level ion accessibility. These issues indicate that MXenes should be regarded not simply as standalone active materials but as multifunctional building blocks for composite electrode design. This review discusses recent progress in MXene-based composite anodes for SIBs, focusing on MXene/carbon composites, MXene/metal compound composites, polymer-assisted composites, and three-dimensional structured MXene composites for improving structural stability, interfacial chemistry, and sodium-storage kinetics. We emphasize that composite engineering can reshape sodium storage from diffusion-limited intercalation toward hybrid mechanisms involving interfacial adsorption, pseudocapacitive storage, heterointerface-driven redox reactions, ion desolvation regulation, and solid-electrolyte interphase stabilization. Key practical challenges, including oxidation control, initial Coulombic efficiency, high-mass-loading electrode design, gravimetric–volumetric performance trade-offs, scalable synthesis, and full-cell validation, are also discussed. Finally, we propose future design principles based on integrated materials chemistry, interfacial science, multiscale architecture engineering, and realistic cell-level evaluation for advancing MXene composites toward practical SIB anodes. Full article

The oxygen evolution reaction (OER) is a key kinetic bottleneck in water electrolysis because it involves multistep proton-coupled electron transfer, the evolution of oxygen-containing intermediates and O–O bond formation. MXenes, as two-dimensional transition-metal carbides, nitrides and carbonitrides, possess high electrical conductivity, hydrophilic surfaces, tunable surface terminations and adjustable layered structures, making them promising platforms for OER catalyst design. However, their limited intrinsic active sites, sheet restacking and oxidative instability under anodic conditions restrict their direct application. This review firstly discusses the fundamental OER pathways based on the adsorbate evolution mechanism (AEM), lattice oxygen mechanism (LOM) and oxide path mechanism (OPM), providing a mechanistic basis for understanding intermediate adsorption, oxygen activation and working-state evolution. Then, a system framework from low-dimensional and micro-level control to high-dimensional and macro-level integration is constructed. The framework covers four levels: atom and local structure, interface, morphology and composite electrode. Drawing on specific examples, this review analyzes the characteristics and mechanisms of modification strategies from four different perspectives, starting with the basic principles of modification. These strategies include micro-scale, low-dimensional approaches such as “Vacancy and other atomic-Level Regulation”, macro-scale, high-dimensional methods like “Composite Engineering”, as well as intermediate approaches involving “Interface engineering” and “morphology engineering”. Special emphasis is placed on distinguishing between beneficial surface reconstruction of catalytically active hydroxyl oxide species and destructive oxidation. Finally, the review identified the unresolved key challenges, including the fuzziness of active sites, the diversity of initial material states and the lack of stability under industrial conditions, and looked forward to the future direction of reasonable design, operational characterization and device-level evaluation. Through this cross-scale analysis, this review aims to clarify the relationship between structure–activity–stability, and provide practical guidance for designing efficient, durable and experimentally verifiable MXene-based OER electrodes. Full article

With the rapid advancement of portable wearable electronics, flexible supercapacitors have ushered in new development opportunities. In recent years, MXene and its composites have demonstrated potential as advanced supercapacitor electrode materials due to their outstanding theoretical capacitance, specific surface area, conductivity, hydrophilicity, and mechanical flexibility. This review traces the development of MXene and summarizes common synthesis strategies, with a focus on the effects of different preparation methods on its structure and properties. Departing from previously reported work, this review draws from the practical requirements of flexible supercapacitors to conduct an in-depth analysis of the key factors influencing the charge storage, rate capability, cycling life, and mechanical flexibility of the devices. It summarizes common design strategies for MXene composites currently used to enhance device performance. Additionally, this study analyzes key challenges facing MXene-based electrode materials, including issues such as self-stacking of layers, insufficient oxidation stability, limited energy density, and structural degradation under complex deformation conditions. Mitigation strategies are summarized, including optimizing synthesis methods and constructing composite systems integrating carbon materials, conducting polymers, and transition metal compounds. Finally, future research directions for MXene in flexible energy storage are explored, emphasizing the need to achieve a balance between performance and manufacturability through synergistic regulation at structural design, interfacial engineering, and device levels. This review aims to provide theoretical guidance for the development of practical MXene-based wearable energy storage devices. Full article

The increasing global demand for high-performance, reliable, and sustainable energy storage systems has accelerated the development of supercapacitors as technologies capable of bridging the performance gap between conventional capacitors and batteries. Supercapacitors combine rapid charge–discharge capability, high power density, and exceptional cycle life through charge storage mechanisms based on ion adsorption and fast surface redox reactions at the electrode–electrolyte interface. This review examines the fundamental operating principles, charge storage mechanisms, electrode materials, mechanical and functional properties, fabrication methods, and engineering applications of modern supercapacitors. Carbon-based materials, metal oxides, conducting polymers, MXenes, sulfides, nitrides, borides, and emerging hybrid systems are critically compared in terms of capacitance, energy density, cycling stability, and mechanical robustness. Additionally, recent advances in scalable manufacturing approaches, including thin-film deposition and printing technologies, are discussed alongside key challenges such as limited energy density, interfacial instability, mechanical degradation, electrolyte compatibility, and large-scale processing. By consolidating recent developments across materials science, electrochemistry, and device engineering, this review provides insight into future directions for next-generation high-performance supercapacitor technologies. Full article

Metal–organic frameworks (MOFs) exhibit high specific surface area and porosity, which may facilitate electron transfer during electrochemical reactions. Therefore, it is clear that MOFs are promising materials for the development of electrochemical sensors. In particular, zinc (Zn) based MOFs offer several advantages such as high specific surface area, porosity, environmental friendliness and low cost. Thus, Zn-based MOF materials and their composites have been extensively utilized in the detection of various pollutants, biomolecules and food additives. The Zn-MOF-based materials have been extensively utilized in electrochemical and fluorescence sensing applications. Previously, various Zn-MOF-based sensing systems such as pristine Zn-MOF, carbon-supported Zn-MOF composites, MXene hybrids with Zn-MOF, and bimetallic/trimetallic Zn-based MOFs were explored to enhance sensing performance. Such materials exhibit remarkable analytical performance, such as a low limit of detection (LOD) (nM to pM range), wide linear response range (LR), fast response times, and high selectivity in the presence of interfering species. In electrochemical sensing, Zn-MOF-modified electrodes demonstrated improved charge-transfer kinetics and sensitivity, enabling accurate determination of the biomolecules, drugs and heavy metal ions in real samples. Similarly, Zn-MOF-based fluorescence sensors showed high luminescent properties and displayed sensitive detection of pollutants and biomolecules. Despite such promising sensing performances, some challenges, such as low stability, reproducibility and selectivity in real-time monitoring, etc., remain that need to be overcome. This review article summarizes the previously reported literature on the fabrication of Zn-MOFs, their composites and Zn-MOF-derived materials for the development of electrochemical and fluorescence sensors. We have also discussed the future directions for the rational design of the high-performance Zn-MOF-based sensing systems for environmental and biomedical applications. We believe that the present review article would be useful for the scientific community working on the fabrication of Zn-MOF-based sensors. Full article

Electrochemical sensors have emerged as promising tools for rapid pesticide screening in food and environmental samples because they combine simple instrumentation, fast response, portability, and compatibility with disposable electrodes. This review organizes recent progress through a cross-system framework linking pesticide class, interfacial electrochemical process, and material design. Carbon materials, metal–organic frameworks and their derivatives, metal nanoparticles, metal compounds, conducting polymers, MXene-based composites, and selected emerging materials are compared in terms of enrichment capability, charge-transfer regulation, catalytic amplification, recognition-layer integration, and suitability for real-sample analysis. Emphasis is placed on issues that are often under-discussed in performance-centered surveys, including matrix interference, electrode fouling, batch-to-batch reproducibility, storage stability, scalability, and cost-effectiveness. Representative examples show that the most useful advances arise not simply from lowering the limit of detection but from improving structure–function understanding and translating interfacial design into robust analytical performance. Future work should prioritize standardized fabrication and benchmarking protocols, in situ and operando identification of active sites and interface evolution, matrix-specific antifouling validation, multiresidue and metabolite analysis, and hybrid portable devices coupled with intelligent readout. Full article

Innovations in nanomaterial science, engineering and printing technologies have increasingly driven advances in electrochemical sensing. Screen-printed electrodes (SPEs) have become a versatile, low-cost, and scalable solution for developing portable electrochemical detection platforms. However, their analytical performance remains intrinsically limited by surface area, electron transfer efficiency, and the immobilization of biomolecules. Recent developments in nanostructured materials, ranging from two-dimensional (2D) materials such as graphene, MXenes, and transition metal dichalcogenides, to one-dimensional nanostructures and hybrid nanocomposites, have transformed the signal transduction landscape of SPE-based electrochemical sensors. Integration of nanomaterials into SPEs has successfully transformed their analytical capabilities, but the diversity of materials and modification strategies has made it difficult to consolidate current knowledge in the field. Strategies that integrate nanomaterials via ink formulation, surface modification, or in situ growth have yielded sensors with unprecedented sensitivity, reproducibility, and selectivity across various chemical and biological targets. This review offers a cross-material synthesis of how nanomaterial engineering transforms the electrochemical performance of SPEs. By integrating insights across morphology, interfacial chemistry, and device-level behavior, it establishes a unified perspective that has been missing from the current literature and clarifies the design principles driving next-generation SPE-based sensing platforms. Full article

The demand for high-performance energy storage systems with enhanced energy and power density is growing alongside the renewable energy, mobile devices, and electric vehicle sectors. MXenes, a class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, have emerged as promising electrode materials for next-generation energy storage systems owing to their high electrical conductivity, hydrophilicity, and tunable surface chemistry. This review provides a comprehensive analysis of recent progress in MXene-based energy storage systems, focusing on MXene synthesis routes, their performance in energy storage applications, associated challenges, and future research directions. It discusses the advantages and disadvantages of various MXene synthesis routes and MXene-based composites, defect engineering, and MXene oxidation, which are crucial for energy storage applications, including rechargeable batteries and supercapacitors. The review also explores the challenges and prospects of scaling up MXenes and their composites for energy storage applications and the existing obstacles to integrating these materials into energy storage systems, with the aim of developing next-generation energy storage systems. Full article

Two-dimensional Ti₃C₂O₂ MXene has emerged as a promising electrode material for non-enzymatic glucose sensing due to its metallic conductivity and biocompatibility. However, the atomic-scale sensing mechanism remains unclear. This DFT study uses the PBE functional with the D3(BJ) dispersion correction to elucidate glucose–MXene interactions under idealized vacuum conditions. Pristine Ti₃C₂O₂ shows metallic behavior with a density of states of about 8.2 states per electron volt at the Fermi level, dominated by Ti 3d states. β-d-glucose adsorbs onto the surface through hydrogen bonding, with an adsorption energy of −0.82 eV at a separation distance of 2.8 angstroms. Bader analysis indicates a transfer of about 0.15 electrons from MXene to glucose, resulting in a Fermi level shift of about −0.15 eV and an 18% reduction in the density of states at the Fermi level. These changes correspond to an estimated sensitivity of approximately 0.6 μA mM⁻¹ cm⁻² and a detection limit of about 17 µM, consistent with reported experimental performance of MXene-based sensors. Comparative adsorption calculations for common sweat interferents yield −0.45 eV for lactate and −0.25 eV for urea, indicating weaker interfacial affinity than glucose; these values reflect thermodynamic binding strength and possible surface occupation rather than definitive electrochemical selectivity, which additionally depends on redox potential, electron-transfer kinetics, and operating bias. We acknowledge three main limitations: first, the model considers only pure oxygen termination rather than mixed oxygen, hydroxyl, and fluorine terminations; second, the calculations are performed under vacuum rather than in aqueous conditions; third, the study is based on static zero kelvin structures rather than finite temperature dynamics. Despite these idealizations, the results provide baseline mechanistic insights to support rational design of MXene-based glucose sensors. Full article

Aqueous supercapacitors are a class of crucial high-power, long-life, safe and reliable energy storage devices, with their performance fundamentally dependent on electrode materials. Two-dimensional (2D) vanadium-based MXenes, possessing rich multivalent redox activity and tunable layered structures, have emerged as one of highly promising electrode candidates, exhibiting significantly superior specific capacitance and pseudocapacitive properties compared to conventional Ti₃C₂T_z. To overcome inherent limitations in conductivity and structural stability, this review summarizes strategies for regulating composition and microstructure through transition metal solid solution and medium-/high-entropy design. These approaches synergistically optimize electron conduction, expand ion migration pathways, and suppress electrode degradation, thereby comprehensively enhancing rate performance, cycle life, and energy density. This review systematically reveals the composition–structure–performance relationships, providing critical design insights and theoretical foundations for developing next-generation high-performance, long-life aqueous MXene-based supercapacitors. Full article

In this study, the structural and electrochemical performance of Nb₂CT_x MXene-based composite electrodes modified with activated carbon (AC) derived from food waste was systematically investigated for supercapacitor applications. Three composites with Nb₂CT_x:AC mass ratios of 90:10 (MXAC1), 80:20 (MXAC2), and 70:30 (MXAC3) were prepared and comparatively evaluated. SEM/EDS, XRD, HR-TEM, XPS, and BET analyses revealed that, in the MXAC2 composite, activated carbon was homogeneously distributed between the MXene layers, effectively suppressing restacking and promoting the formation of a hierarchical micro/mesoporous structure. XPS results confirmed the preservation of the Nb–C framework and the enrichment of surface functional groups (–O, –OH, and –F). BET analysis demonstrated that MXAC2 possesses an optimized pore architecture that facilitates efficient ion diffusion. Electrochemical measurements revealed that the MXAC2 electrode exhibited the highest specific capacitance at all scan rates and current densities. At 5 mV·s⁻¹, MXAC2 achieved a specific capacitance of 651.84 F·g⁻¹ and maintained a substantial capacitance even at a high current density of 4 A·g⁻¹. EIS analysis confirmed the very low charge transfer resistance (0.023 Ω) and enhanced capacitive behavior for MXAC2. Additionally, MXAC2 has high cycle stability, demonstrating 82.15% capacitive retention and 92.45% coulombic efficiency after 10000 cycles. These results indicate that food waste-derived AC-optimized Nb₂CT_x MXene composite materials are a strong candidate for sustainable and high-performance supercapacitor electrodes. Full article

The future growth of alkali metal-based batteries requires an understanding of how ion size affects the exchange mechanisms. In this work, we present a direct, comparative electrochemical study of MXene-based electrodes mechanism vs. lithium (Li⁺), sodium (Na⁺), and potassium (K⁺) ions using the same electrochemical conditions. This controlled method enables an extensive investigation of the size-dependent interactions between the MXene structure and alkali metal ions. X-ray photoelectron spectroscopy and Raman analysis of TMAOH-treated Ti₃C₂T_x MXene electrodes show that delamination and cycling alter vibrational modes and the surface chemistry. Voltage profile study reveals diverse storage behaviors: Li⁺ has a prominent intercalation plateau, Na⁺ shows intermediate properties, and K⁺ displays sloping profiles, indicating surface-dominated adsorption. The significant correlation between ionic radius and electrochemical reversibility is shown by long-term cycling data over 300 cycles, which show greater capacity retention and stability for Li⁺ and progressively lower performance for Na⁺ and K⁺. These findings provide new mechanistic insights into MXene–ion interactions and build the foundation for developing MXene-based materials for specific alkali-ion chemistries in next-generation energy storage devices. Full article

Silicon (Si) has attracted extensive attention as a promising anode material for next-generation lithium-ion batteries (LIBs) due to its ultra-high theoretical capacity, low lithiation potential, and economic advantages. However, drastic volume expansion during cycling and slow reaction kinetics severely compromise its structural stability and practical application. Recently, two-dimensional (2D) MXenes have been explored as effective functional components in Si-based electrodes because of their excellent electrical conductivity, high specific surface area, adjustable surface terminations, and mechanical robustness. When integrated with Si, MXenes serve as conductive matrices that alleviate volumetric stress, enhance charge transport, and accelerate electron/ion diffusion. Consequently, Si/MXene nanocomposites (NCs) exhibit significantly improved lithium (Li) storage performance. This review outlines recent advances in Si/MXene NCs, covering fabrication strategies, structural engineering, and various configurations, including particulate materials, three-dimensional (3D) architectures, films, and fibrous systems, and establishes the relationship between structural design and electrochemical behavior. Remaining challenges and prospective research directions are also discussed to guide the development of high-energy-density LIB anodes. Full article

V₂CT_x MXene is a promising anode material for lithium-ion batteries due to its high electrical conductivity and abundant active sites. However, the spatial environment within its layers restricts the function of its energy storage electrode. Herein, V₂CT_x MXene was synthesized via an NH₄F–HCl-assisted hydrothermal etching method, followed by electrochemical pre-intercalation of Mn²⁺ using a three-electrode system. Structural characterizations confirm that Mn²⁺ pre-intercalation effectively modulates the interlayer environment, reduces surface F terminations, and maintains a stable layered structure. Electrochemical measurements demonstrate that the Mn²⁺-intercalated V₂CT_x MXene delivers an enhanced reversible capacity of 313.6 mAh·g⁻¹ after 200 cycles, outperforming pristine V₂CT_x MXene. The improved rate capability and reduced charge transfer resistance indicate accelerated ion/electron transport kinetics. This study provides an effective interlayer engineering strategy for improving MXene-based lithium-ion storage performance. Full article