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Since the form of the exact functional in density functional theory is unknown, we must rely on density functional approximations (DFAs). In the past, very promising results have been reported by combining semi-local DFAs with exact, i.e. Hartree–Fock, exchange. However, the spin-state energy ordering and the predictions of global minima structures are particularly sensitive to the choice of the hybrid functional and to the amount of exact exchange. This has been already qualitatively described for single conformations, reactions, and a limited number of conformations. Here, we have analyzed the mixing of exact exchange in exchange functionals for a set of several hundred isomers of the transition metal carbide, Mo4C2. The analysis of the calculated energies and charges using PBE0-type functional with varying amounts of exact exchange yields the following insights: (1) The sensitivity of spin-energy splitting is strongly correlated with the amount of exact exchange mixing. (2) Spin contamination is exacerbated when correlation is omitted from the exchange-correlation functional. (3) There is not one ideal value for the exact exchange mixing which can be used to parametrize or choose among the functionals. Calculated energies and electronic structures are influenced by exact exchange at a different magnitude within a given distribution; therefore, to extend the application range of hybrid functionals to the full periodic table the spin-energy splitting energies should be investigated. [ABSTRACT FROM AUTHOR]

Mass-selected photoelectron velocity-map imaging spectroscopy in conjunction with the density functional theory calculations was employed to investigate the geometrical and chemical bonding properties of NiC3−/0. Both the photoelectron spectrum and photoelectron angular distribution were measured from the spectra, yielding useful geometrical and electronic information about NiC3−/0. The complementary theoretical calculations suggest that the linear and fan-like structures were both populated experimentally in the cluster beam. Further comparative study on the synergistic donor–acceptor interactions in both isomers revealed the side-on coordination-induced bond weakening in the fan-like isomer as compared to the linear isomer. These findings will shed light on the structure-dependent reactivity of transition metal carbides. [ABSTRACT FROM AUTHOR]

The application of microwave absorption materials, which can effectively convert electromagnetic energy into thermal energy and/or other forms of energy, can effectively solve the increasingly serious electromagnetic pollution. As a type of promising microwave absorption material, ternary transition metal carbides/nitrides MAX phases possess layered structure and superior conduction loss capability. However, poor impedance matching and single polarization loss type seriously hinder their improvement of microwave absorption performance. High-entropy engineering is expected to be an effective strategy to address the above problems simultaneously. Herein, a series of low-, medium-, and high-entropy MAX phases with Ti2AlC structure were successfully synthesized and their structure, composition, and morphology were comprehensively characterized. High-entropy MAX phase (Ti1/5Zr1/5V1/5Nb1/5Ta1/5)2AlC presents excellent microwave absorption performance with the optimal minimum reflection loss (RLmin) of −47 dB at 11.92 GHz (a thickness of 2.4 mm) and optimal effective absorption bandwidth of 3.92 GHz between 8.48 and 12.4 GHz (a thickness of 2.78 mm), which are better than those of our prepared low-/medium-entropy MAX phases as well as most of the other previously reported MAX phases. Such excellent microwave absorption performance of (Ti1/5Zr1/5V1/5Nb1/5Ta1/5)2AlC is attributed to high-entropy engineering, which not only optimizes the impedance matching through regulating permittivity but also introduces more polarization loss type and amount. This work reveals that high-entropy engineering is not only a workable method to enhance the microwave absorption performance in MAX phases, but also an effective strategy to tailor the balance between impedance matching and loss capability through compositional design in single-phase systems. [ABSTRACT FROM AUTHOR]

The synthesis of hafnium carbide nanowires (HfC NWs) on carbon fibers was successfully achieved by employing HfCl 4 and furfuryl alcohol as precursor materials, facilitated by Ni-assisted catalytic pyrolysis. In the polymerization and cross-linking processes of furfuryl alcohol, hafnium cations play a crucial role, leading to the atomic-level amalgamation and effectively enhancing the reactivity of the Hf-O-C system. The nucleation of HfC NWs takes place at 1300 °C, followed by growth through a solid-liquid-solid (SLS) mechanism. Carbon fibers were uniformly coated with tens micrometer-long HfC NWs having an approximate diameter of 500 nm. Notably, the tips of these HfC NWs exhibited clean surfaces free of Ni catalyst particles, indicating their root growth model. This novel catalyst-assisted pyrolysis method holds great potential for enabling cost-effective large-scale production of transition metal carbide nanowires. [ABSTRACT FROM AUTHOR]

To achieve Si‐free refractory ceramic matrix composites exposed to an oxidizing atmosphere at approximately 2000°C, a Ti–Zr–Mo ternary alloy melt‐infiltration (MI) method was developed for the production of carbon fiber‐reinforced refractory high‐entropy ceramic matrix composites (C/RHECs), with high‐entropy carbides serving as the matrix. This approach was designed using calculation phase diagrams (CALPHADs) and the calculation of thermodynamic parameters. The combination of CALPHAD and the calculation of alloy and carbon reactivity enabled the prediction of reaction and infiltration behavior into a preform comprising carbon fiber, carbon black, and transition metal carbide powders. Furthermore, C/RHECs featuring a (Ti, Zr, Hf, Nb, Ta, Nb, Mo)C matrix were experimentally fabricated through the Ti–Zr–Mo alloy MI method in accordance with the design. The arc‐wind tunnel tests on the C/RHECs conducted at approximately 2000°C revealed surfaces covered with complex oxides. The apparent oxidation rate of the C/RHECs was similar to that of Si‐containing ceramics and composites. These results indicate that complex oxides act as a barrier to oxygen diffusion toward unoxidized regions, making Si no longer essential for protecting materials from oxidation above 2000°C. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D MXenes are the key materials in novel flexible electronic devices. • MXene-based electronics on various substrates (hydrogel, paper, etc.) are reviewed. • MXene-based electronics can be integrated with artificial intelligence. • Applications of MXenes in the new generation of wearable devices are summarized. • Challenges and difficulties in designing MXene-based electronics are discussed. • Future research directions are also suggested for wearable MXene electronics. Wearable electronic devices find increasing applications in mobile medical sensing and monitoring, human–computer interaction, and portable energy collection and storage, owing to their flexibility and stretchability. In recent years, transition metal nitrides and carbides, known as MXenes, have become cornerstones for the preparation of novel flexible electronic devices because of their excellent electrical conductivities, abundant surface functional groups, and large specific surface areas. This review presents the latest developments in MXene-based wearable electronic products, including hydrogels, paper, composite materials, and self-powered devices. These products can be integrated with artificial intelligence to show unique applications in healthcare, inspection, and control of human-like machines. The application prospects of MXenes in the new generation of wearable electronic devices are forecast, the challenges and difficulties in designing MXene-based wearable electronic devices are discussed, and corresponding solutions are suggested. This review also provides future research directions for the development of MXenes for pliable and wearable applications. [ABSTRACT FROM AUTHOR]

Blood stasis syndrome (BSS) has persistent health risks; however, its pathogenesis remains elusive. This obscurity may result in missed opportunities for early intervention, increased susceptibility to chronic diseases, and reduced accuracy and efficacy of treatments. Metabolomics, employing the matrix-assisted laser desorption/ionization (MALDI) strategy, presents distinct advantages in biomarker discovery and unraveling molecular mechanisms. Nonetheless, the challenge is to develop efficient matrices for high-sensitivity and high-throughput analysis of diverse potential biomarkers in complex biosamples. This work utilized nitrogen-doped porous transition metal carbides and nitrides (NP-MXene) as a MALDI matrix to delve into the molecular mechanisms underlying BSS pathogenesis. Structural optimization yielded heightened peak sensitivity (by 1.49-fold) and increased peak numbers (by 1.16-fold) in clinical biosamples. Validation with animal models and clinical serum biosamples revealed significant differences in metabolic fingerprints between BSS and control groups, achieving an overall diagnostic efficacy of 0.905 (95% CI, 0.76–0.979). Prostaglandin F2α was identified as a potential biomarker (diagnostics efficiency of 0.711, specificity = 0.7, sensitivity = 0.6), and pathway enrichment analysis disclosed disruptions in arachidonic acid metabolism in BSS. This innovative approach not only advances comprehension of BSS pathogenesis, but also provides valuable insights for personalized treatment and diagnostic precision. [ABSTRACT FROM AUTHOR]

A new family of two‐dimensional (2D) transition metal carbides, carbonitrides, and nitrides (MXenes) has attracted increasing attention owing to their electrical, chemical, and physical properties. Together with various attractive properties of the MXenes, they also exhibit electrochemical induced deformation (i.e., expansion/contraction) via ion intercalation/de‐intercalation in/from MXene layers. In this respect, MXenes offer the possibility of application as the electrode of electrochemical actuators (ECAs). While the MXene‐based ECAs are still in their infancy stage, researchers have made great effort to achieve high‐performance MXene‐based electrochemical capacitors (ECs). As the name suggests, both ECAs and ECs shared common traits in which their operations are based on electrochemical processes. This review provides the recent progress in the MXene‐based ECAs in parallel with that in the MXene‐based ECs to gain insights from the relatively mature developments in EC applications. Finally, based on the findings from previous studies on both electrochemical applications, perspectives on future MXene‐based ECAs in terms of electrode, electrolyte, and cell configuration are provided. [ABSTRACT FROM AUTHOR]

[Display omitted] Two-dimensional (2D) transition metal carbide and nitride (MXenes) and 2D transition metal borides are analogs to MXenes and are given the name MBenes. MXenes and MBenes are important 2D nanomaterials with diverse potential in various research domains of physics and chemistry. MBenes offer high conductivity, flexibility, and mechanical properties, attracting attention for energy storage applications such as mono/divalent batteries and supercapacitors. Both theoretical and experimental results confirmed the exciting potential of MBene for energy storage applications. MBenes have demonstrated a broad range of fascinating characteristics and have been extensively researched for their potential uses in energy storage and conversion devices. It is reasonable to anticipate that MBenes will have a bright future. The investigation of MBenes, on the other hand, is still in its early stages, and there are a great deal of expected features and applications that are being investigated. This review aims to provide an overview of recent advancements not only in energy storage applications but also in various other aspects, including synthetic methods, morphological and structural characteristics, and other associated properties of MBene. Finally, this critical review ends with the promising prospects, challenges, and opportunities in MBene advancements. [ABSTRACT FROM AUTHOR]

Due to excellent performances and easy adjustability, more and more researchers pay attention to high-entropy ceramics, which can be applied in many fields. In this work, a high-entropy transition metal carbide ceramic, (Hf 0.2 Ta 0.2 Zr 0.2 Nb 0.2 W 0.2)C, was fabricated by pressureless sintering method. To obtain highly dense ceramic, dual sintering aids (Cr 3 C 2 and C), are employed in the sintering process. Owing to suitable microstructure (grain size and defect density), the ceramics exhibit excellent electric conductivity(0.7040 MS/m) and flexural strength (378 ± 11.4 MPa). Meanwhile, the relationship between electromagnetic shielding effectiveness and different aid content in the X-band is also investigated. The P3 ceramic with a thickness of 1 mm can achieve an EMI shielding efficiency of 92 dB in the X-band as a result of the stronger interface polarization and relaxation effects. High-entropy ceramic obtained in this work would give a different way to fabricate shielding material and can promote the use of high-entropy ceramics as effective EMI shielding materials. [ABSTRACT FROM AUTHOR]

The advancement of a sustainable and scalable catalyst for hydrogen production is crucial for the future of the hydrogen economy. Electrochemical water splitting stands out as a promising pathway for sustainable hydrogen production. However, the development of Pt‐free electrocatalysts that match the energy efficiency of Pt while remaining economical poses a significant challenge. This review addresses this challenge by highlighting latest breakthroughs in Pt‐free catalysts for the hydrogen evolution reaction (HER). Specifically, we delve into the catalytic performance of various transition metal phosphides, metal carbides, metal sulphides, and metal nitrides toward HER. Our discussion emphasizes strategies for enhancing catalytic performance and explores the relationship between structural composition and the performance of different electrocatalysts. Through this comprehensive review, we aim to provide insights into the ongoing efforts to overcome barriers to scalable hydrogen production and pave the way for a sustainable hydrogen economy. [ABSTRACT FROM AUTHOR]

Two-dimensional titanium carbides (Ti 3 C 2 T x) are part of the novel family of transition metal carbides/nitrides known as MXenes, which exhibit a broad range of photo-electrocatalytic applications. In this study, we present a facile hydrothermal synthesis method for Ti 3 C 2 T x decorated on molybdenum diselenide (MoSe 2) nanoflower composites, serving as an enhanced catalyst for hydrogen (H 2) evolution. Ti 3 C 2 T x , acting as a 2D conductive substrate, facilitates electron transfer, preventing MoSe 2 agglomeration, while MoSe 2 offers abundant active sites. The characterizations of surface analysis, optical properties, morphological nanostructure, and elemental composition performance of Ti 3 C 2 T x nanosheets, MoSe 2 nanoflowers, and Ti 3 C 2 T x /MoSe 2 nanoflower composites was conducted using FTIR, XRD, UV–Visible spectroscopy, SEM, EDS Mapping, TEM, and XPS techniques. The catalyst with optimal performance, the Ti 3 C 2 T x /MoSe 2 nanoflower composite demonstrates excellent functional properties in the H 2 evolution, showing a lower overpotential of 135 mV and smaller Tafel slope of 72 mV/dec at 10 mA/cm2 compared to Ti 3 C 2 T x nanosheets and MoSe 2 nanoflowers. The Ti 3 C 2 T x /MoSe 2 nanoflower composite forms heterojunctions to inhibit the rapid recombination rate of photo-induced electrons and holes. In comparison to MoSe 2 nanoflowers and Ti 3 C 2 T x catalysts (where T x = F, and O surface terminations), the optimized Ti 3 C 2 T x /MoSe 2 nanoflower composite exhibits significantly enhanced photocatalytic activity in H 2 production, with a H 2 production rate of 2146 μmolg−1h−1 superior than the Ti 3 C 2 T x nanosheets (1367 μmolg−1h−1) and MoSe 2 nanoflowers (986 μmolg−1h−1), respectively. Through this design, effective separation of photogenerated charge carriers is achieved, improving the activity of photocatalytic H 2 production and demonstrating the promise of the cocatalyst strategy for photocatalysis. [ABSTRACT FROM AUTHOR]

The development of spintronic devices urgently requires ultra-thin two-dimensional (2D) ferromagnetic materials with high Curie temperature (Tc), TC however, there are few natural intrinsic ferromagnetic 2D materials. The successful synthesis of Janus monolayer MoSSe in experiments provides a new approach for designing new 2D materials. By replacing transition metal carbides with two different transition metal atoms, we have designed over 70 Janus MXence materials and determined that 30þ materials have ferromagnetic ground states, of which three have robust ferromagnetism through density functional theory analysis. The ferromagnetic coupling in suchmaterials mainly originates from the direct exchange of d-orbitals between transition metal atoms in different layers. Further, using K-nearest neighbours (KNN) machine learning (ML) method, six out of the remaining 360 Janus MXence systems were screened for ferromagnetism, with one system exhibiting strong ferromagnetism. This work provides an alternative and convenient method for developing ultra-thin 2D magnetic materials for next generation spintronic device applications. [ABSTRACT FROM AUTHOR]

Transition metal carbides (TMCs) are a class of materialswith excellent dielectric properties and thermal stability, which exhibit enormous potential in high temperature electromagnetic wave absorption (EWA). However, the high dielectric constant and electrical conductivity of TMCs usually cause impedance mismatch, and their high density also prevents further practical applications. To solve these problems, the lightweight and impedance matching NbC nanowires (NbCnws) were prepared by using bamboo powder as a carbon source and subsequent carbothermal reduction reaction process. The as-synthesized NbCnws all exhibit a low density of 0.23 g/cm³ and superior EMA performance. It is worth noting that the minimum reflection loss (RLmin) of the sample is -43.03 dB at 5.92 GHz and the corresponding matching thickness is only 3.7 mm when sintering temperature is 1500°C. The excellent electromagnetic wave absorption (EWA) performance is attributed to good impedance matching and strong dielectric loss. This research work provides a prospect for the development and utilization of one-dimensional TMC materials in the field of microwave absorption materials. [ABSTRACT FROM AUTHOR]

Biological macroporous materials, such as stems of the plants and bone of the animals, possess outstanding properties for powerful guarantee of creatures' survival through the well‐aligned architecture constructed from limited components. Transition metal carbides or nitrides (MXenes), as novel 2D assemblies, have attracted numerous attentions in various applications due to their unique properties. Therefore, mimicking the bioinspired architecture with MXenes will boost the development of human‐made materials with unparalleled properties. Freeze casting has been widely applied to fabricate bioinspired MXene‐based materials and achieve the assembly of MXene nanosheets into 3D forms. This process solves the inherent restacking problems of MXenes, simultaneously preserving the unique properties of MXenes with a physical process. Here, the ice‐templated assembly of MXene in terms of the freezing processes and their potential mechanisms is summarized. In addition, applications of MXene‐based materials in electromagnetic interference shielding and absorption, energy storage and conversion, as well as piezoresistive pressure sensors are also reviewed. Finally, the current challenges and bottlenecks of ice‐templated assembly of MXene are further discussed to guide the development of bioinspired MXene‐based materials. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal carbides/nitrides (MXenes) are emerging members of the two-dimensional material family, obtained by removing the A layer of the MAX phase through methods such as liquid-phase etching. This article summarizes the structure and properties of MXenes, as well as several preparation methods, including etching with hydrofluoric acid and fluoride salts, alkali-based etching, electrochemical etching, Lewis acid molten salt etching, and direct synthesis. Due to their unique two-dimensional structure and surface chemistry, MXenes exhibit good metallic conductivity, hydrophilicity, excellent flexibility, and ion intercalation properties, showing great potential in the research and application of supercapacitors and attracting widespread attention. The combination of MXene with other types of materials, including polymers, metal hydroxides, metal oxides, and carbon materials, takes advantage of composites to improve energy storage performance and shows great potential in the research and application of supercapacitors. This article provides a detailed summary of MXene composite materials and capacitor performance and introduces the research progress of MXene materials in the field of supercapacitor energy storage applications, aiming to provide references for the preparation of high-performance MXene supercapacitor electrode materials. [ABSTRACT FROM AUTHOR]

The Ru-V 8 C 7 /C electrocatalyst has been synthesized by anchoring Ru nanoparticles on the porous V 8 C 7 /C matrix via pyrolysis of metal organic-frameworks V-BDC (BDC: 1,4-benzenedicarboxylate), exhibiting excellent HER performance in all pH ranges, especially the high mass activities and long-term stability under neutral conditions. [Display omitted] The development of cost-effective electrocatalysts with high efficiency and long durability for hydrogen evolution reaction (HER) remains a great challenge in the field of water splitting. Herein, we design an ultrafine and highly dispersed Ru nanoparticles stabilized on porous V 8 C 7 /C matrix via pyrolysis of the metal–organic frameworks V-BDC (BDC: 1,4-benzenedicarboxylate). The obtained Ru-V 8 C 7 /C composite exhibits excellent HER performance in all pH ranges. At the overpotential of 40 mV, its mass activity is about 1.9, 4.1 and 9.4 times higher than that of commercial Pt/C in acidic, neutral and alkaline media, respectively. Meanwhile, Ru-V 8 C 7 /C shows the remarkably high stability in all pH ranges which, in particular, can maintain the current density of 10 mA cm−2 for over 150 h in 1.0 mol L−1 phosphate buffer saline (PBS). This outstanding HER performance can be attributed to the high intrinsic activity of Ru species and their strong interface interactions to the V 8 C 7 /C substrate. The synergistic effect of abundant active sites on the surface and the formed Ru–C–V units at the interface promotes the adsorption of reaction intermediates and the release of active sites, contributing the fast HER kinetics. This work provides a reference for developing versatile and robust HER catalysts by surface and interface regulation for pH tolerance. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) layered materials demonstrate prominent advantage in regulating lithium plating/stripping behavior by confining lithium diffusion/plating within interlayer gaps. However, achieving effective interlayer confined lithium diffusion/plating without compromising the stability of bulk‐structural and the solid electrolyte interphase (SEI) remains a considerable challenge. This paper presents an electrochemical scissor and lithium zipper‐driven protocol for realizing interlayer confined lithium plating with pretty‐low strain and volume change. In this protocol, lithium serves as a "zipper" to reunite the adjacent MXene back to MAX‐like phase to markedly enhance the structural stability, and a lithium halide‐rich SEI is formed by electrochemically removing the terminals of halogenated MXenes to maintain the stability and rapid lithium ions diffusion of SEI. When the Ti3C2I2 serves as the host for lithium plating, the average coulomb efficiency exceeds 97.0 % after 320 lithium plating/stripping cycles in conventional ester electrolyte. Furthermore, a full cell comprising of LiNi0.8Mn0.1Co0.1O2 and Ti3C2I2@Li exhibits a capacity retention rate of 73.4 % after 200 cycles even under high cathode mass‐loading (20 mg cm−2) and a low negative/positive capacity ratio of 1.4. Our findings advance the understanding of interlayer confined lithium plating in 2D layered materials and provide a new direction in regulating lithium and other metal plating/stripping behaviors. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) layered materials demonstrate prominent advantage in regulating lithium plating/stripping behavior by confining lithium diffusion/plating within interlayer gaps. However, achieving effective interlayer confined lithium diffusion/plating without compromising the stability of bulk‐structural and the solid electrolyte interphase (SEI) remains a considerable challenge. This paper presents an electrochemical scissor and lithium zipper‐driven protocol for realizing interlayer confined lithium plating with pretty‐low strain and volume change. In this protocol, lithium serves as a "zipper" to reunite the adjacent MXene back to MAX‐like phase to markedly enhance the structural stability, and a lithium halide‐rich SEI is formed by electrochemically removing the terminals of halogenated MXenes to maintain the stability and rapid lithium ions diffusion of SEI. When the Ti3C2I2 serves as the host for lithium plating, the average coulomb efficiency exceeds 97.0 % after 320 lithium plating/stripping cycles in conventional ester electrolyte. Furthermore, a full cell comprising of LiNi0.8Mn0.1Co0.1O2 and Ti3C2I2@Li exhibits a capacity retention rate of 73.4 % after 200 cycles even under high cathode mass‐loading (20 mg cm−2) and a low negative/positive capacity ratio of 1.4. Our findings advance the understanding of interlayer confined lithium plating in 2D layered materials and provide a new direction in regulating lithium and other metal plating/stripping behaviors. [ABSTRACT FROM AUTHOR]

2D transition metal carbide/nitride heterostructures are emerging pseudocapacitive materials for supercapacitors (SCs); however, the lack of efficient synthesis methods and an in‐depth understanding of the pseudocapacitive storage mechanism of these potentially important materials impede their applications in SCs. Herein, 2D MoN/MoC nanosheets with a precisely regulated interface are prepared controllably by a scalable salt‐assisted method with bulk MoS2 as the precursor. In operando infrared spectroscopy and electrochemical quartz crystal microbalance results reveal that the pseudocapacitance of the MoN/MoC nanosheets originates from the reversible reaction between Mo–N sites and H+ in the acidic electrolyte. Density‐functional theory calculations and X‐ray photoelectron spectroscopy disclose that the MoC/MoN heterointerface induces the internal electric field from the accumulated negative charges at the Mo–N sites by electron donation from MoC, leading to enhanced H+ adsorption at the Mo–N sites and superior pseudocapacitive storage. The heterostructured MoN/MoC nanosheets show a large volumetric capacity of 1045.3 F cm−3 at 1 A cm−3, high‐rate capability of 702.8 F cm−3 at 10 A cm−3, and superior cyclability with capacity retention of 98% after 10,000 cycles, which outperform reported Mo‐based carbides and nitrides. The results provide new insights into the development of high‐performance 2D heterostructured materials for superior pseudocapacitive storage. [ABSTRACT FROM AUTHOR]

MXenes are two-dimensional transition metal carbides, nitrides, and carbonitrides that have become important materials in nanotechnology because of their remarkable mechanical, electrical, and thermal characteristics. This review emphasizes how crucial MXene conjugates are for several biomedical applications, especially in the field of cancer. These two-dimensional (2D) nanoconjugates with photothermal, chemotherapeutic, and photodynamic activities have demonstrated promise for highly effective and noninvasive anticancer therapy. MXene conjugates, with their distinctive optical capabilities, have been employed for bioimaging and biosensing, and their excellent light-to-heat conversion efficiency makes them perfect biocompatible and notably proficient nanoscale agents for photothermal applications. The synthesis and characterization of MXenes provide a framework for an in-depth understanding of various fabrication techniques and their importance in the customized formation of MXene conjugates. The following sections explore MXene-based conjugates for nanotheranostics and demonstrate their enormous potential for biomedical applications. Nanoconjugates, such as polymers, metals, graphene, hydrogels, biomimetics, quantum dots, and radio conjugates, exhibit unique properties that can be used for various therapeutic and diagnostic applications in the field of cancer nanotheranostics. An additional layer of understanding into the safety concerns of MXene nanoconjugates is provided by detailing their toxicity viewpoints. Furthermore, the review concludes by addressing the opportunities and challenges in the clinical translation of MXene-based nanoconjugates, emphasizing their potential in real-world medical practices. [ABSTRACT FROM AUTHOR]

[Display omitted] As an emerging class of layered transition metal carbides/nitrides/carbon-nitrides, MXenes have been one of the most investigated anode subcategories for sodium ion batteries (SIBs), due to their unique layered structure, metal-like conductivity, large specific surface area and tunable surface groups. In particular, different MAX precursors and synthetic routes will lead to MXenes with different structural and electrochemical properties, which actually gives MXenes unlimited scope for development. In this feature article, we systematically present the recent advances in the methods and synthetic routes of MXenes, together with their impact on the properties of MXenes and also the advantages and disadvantages. Subsequently, the sodium storage mechanisms of MXenes are summarized, as well as the recent research progress and strategies to improve the sodium storage performance. Finally, the main challenges currently facing MXenes and the opportunities in improving the performance of SIBs are pointed out. [ABSTRACT FROM AUTHOR]

MXenes are a promising class of two‐dimensional transition metal carbides, nitrides, and carbonitrides, widely utilized in diverse fields such as energy storage, electromagnetic shielding, electrocatalysis, and sensing applications. Their potential in chemical sensing is particularly noteworthy, where optimizing surface chemistry for strong interaction with target analytes and increasing surface area for efficient gas adsorption are crucial factors. In this study, a versatile and general self‐assembly method for fabricating nanometer‐scale thin films of surface‐functionalized MXene, enabling high‐performance gas sensors is developed. By dropping MXene dispersed in organic solvents onto nonsolvents, rapid formation of nanometer‐scale films is achieved. This method allows easy adjustment of film properties by using different solvent‐nonsolvent combinations, leading to improved optoelectronic properties compared to conventional techniques. The surface‐functionalized MXenes using ADOPA ligands greatly enhance the gas response and long‐term environmental stability compared to pristine MXenes. Computational methods are also employed to gain insights into the molecular interactions and changes in electronic structure that contribute to the enhanced sensing properties. Furthermore, the environmental stability of MXene sensors is largely enhanced after surface functionalization, which can be attributed to increased surface hydrophobicity. Overall, this innovative technique opens up opportunities for tailoring MXene thin films for specific applications. [ABSTRACT FROM AUTHOR]

Graphene and two-dimensional transition metal carbides and/or nitrides (MXenes) are important materials for making flexible energy storage devices because of their electrical and mechanical properties. It remains a challenge to assemble nanoplatelets of these materials at room temperature into in-plane isotropic, free-standing sheets. Using nanoconfined water-induced basal-plane alignment and covalent and π-π interplatelet bridging, we fabricated Ti3C2Tx MXene-bridged graphene sheets at room temperature with isotropic in-plane tensile strength of 1.87 gigapascals and moduli of 98.7 gigapascals. The in-plane room temperature electrical conductivity reached 1423 siemens per centimeter, and volumetric specific capacity reached 828 coulombs per cubic centimeter. This nanoconfined water-induced alignment likely provides an important approach for making other aligned macroscopic assemblies of two-dimensional nanoplatelets. [ABSTRACT FROM AUTHOR]

Hydrogen, known for its renewable nature, high energy utilization efficiency, and clean combustion, holds significant importance as a component in future energy systems. However, the development of an economical, safe, and efficient method for hydrogen storage remains a formidable challenge. In recent decades, researchers have made significant progress in achieving reversible hydrogen absorption and release using various metal hydrides. Among them, magnesium hydride (MgH 2) has attracted considerable attention for its high energy density, low cost, and good reversibility. Nevertheless, the high hydrogen absorption and desorption temperature, sluggish kinetic properties, and poor cycling performance of MgH 2 remain as the bottlenecks for its practical application. To mitigate these deficiencies, significant research efforts have been focused on the development of carbon-based materials as a means of preparing multifunctional materials. Carbon-based materials have demonstrated great potential in facilitating synergistic modification strategies, such as nanosizing, catalytic effects, and spatial confinement, which have been proven effective in enhancing the hydrogen storage performance of MgH 2. In this paper, we present a comprehensive overview of various carbon-based materials, highlighting their unique properties and their contribution to improving hydrogen storage within MgH 2 matrices. To be specific, we have been systematically reviewed the synergistic impacts of carbon materials, metal-organic frameworks, transition metal carbides (MXenes), and their respective composites on enhancing the hydrogen storage performance of MgH 2. Additionally, this study underscores the benefits of utilizing multifunctional carbon-based materials as modifiers for MgH 2 and proposes potential avenues for academic research. [Display omitted] • The properties and benefits of various carbon-based materials has been comprehensively reviewed. • Carbon-based materials and their roles in improving the hydrogen storage of MgH 2 have been thoroughly investigated. • The promise of multifunctional carbon-based materials as modifiers for MgH 2 is highlighted. • The future directions of carbon-based materials in hydrogen storage are discussed. [ABSTRACT FROM AUTHOR]

Transition metal carbides (TMCs) have emerged as highly intriguing materials for CO2 hydrogenation, primarily due to their excellent ability on CO2 adsorption and activation, strong metal‐support interaction (SMSI), as well as the engineered metal/TMCs or TMCs/substrate interfaces for fine‐tuning of activity and selectivity. In this review, the strategies of modulating the structure and properties of TMCs to attain desirable products in CO2 hydrogenation are discussed from the following perspectives: 1) Manipulation of metal/C ratios or atomic arrangements; 2) Incorporation of heteroatom on TMCs to construct TMCs composites; 3) Enhancement of TMC nanoparticles dispersion; 4) In situ generation of TMCs induced by reactions. Such strategies in TMC structural engineering are key factors affecting the catalytic behaviors of TMCs and provide fundamental understanding and guidance for the future application of TMCs in CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

The designing of electrocatalyst to perform hydrogen evolution reaction (HER) in alkaline medium is presently a demanding pathway for sustainable production of hydrogen (H 2) which can be generated from alkaline water electrolysis used in industries. Although a large number of electrocatalyst reported in literature have the tendency to exhibit superior HER performance in acidic medium, but the vaporization of acid electrolyte causes corrosion of the cell and resulted in contamination during the H 2 production. The involvement of additional step during water dissociation process (volmer step) in alkaline medium could cause serious sluggish electrode kinetics and thus a hunt of new type of heterostructured electrocatalyst (to indue strong synergetic effect of the heterointerfaces) to outperform noble precious metals are under exploration. The development of earth abundant transition metal carbides/phosphides have been emerging recently because of their electronic structure/configuration are similar to that of platinum (Pt), leading to enhance the elecrocatalytic performance. A variety of metallic carbides/phosphides incorporated on porous materials are studied by researchers are faced difficulty in integration of single nanostructure unit to achieve HER activity in alkaline medium as same as that in acidic medium. The present review aims to provide comprehensive of heterostructured carbides/phosphides supported on N-doped porous carbon (NPC) for electrocatalytic efficiency for HER. We also discussed the influencing role of structure, codopants, and the porosity for lowering overpotentials. Finally, the challenges and the future goals for designing efficient electrocatalyst to provide promising HER for large scale applications are highlighted. • The review article focuses on metallic carbides/phosphides embedded in N-doped porous carbon as electrocatalyst. • The demonstration of electrocatalyst towards HER in alkaline medium are discussed. • The role of dopants, structure and the porosity for reducing the overpotential of HER are summarized. • Recent developments, challenges and future perspectives have also been reviewed. • The first review on metallic carbides/phosphides as electrocatalyst for HER in alkaline medium. [ABSTRACT FROM AUTHOR]

2D transition metal carbides and nitrides (MXenes) suggest an uncommonly broad combination of important functionalities amongst 2D materials. Nevertheless, MXene suffers from facile oxidation and colloidal instability upon conventional water‐based processing, thus limiting applicability. By experiments and theory, It is suggested that for stability and dispersibility, it is critical to select uncommonly high permittivity solvents such as N‐methylformamide (NMF) and formamide (FA) (εr = 171, 109), unlike the classical solvents characterized by high dipole moment and polarity index. They also allow high MXene stacking order within thin films on carbon nanotube (CNT) substrates, showing very high Terahertz (THz) shielding effectiveness (SE) of 40–60 dB at 0.3–1.6 THz in spite of the film thinness < 2 µm. The stacking order and mesoscopic porosity turn relevant for THz‐shielding as characterized by small‐angle X‐ray scattering (SAXS). The mechanistic understanding of stability and structural order allows guidance for generic MXene applications, in particular in telecommunication, and more generally processing of 2D materials. [ABSTRACT FROM AUTHOR]

Researchers have been looking for prominent materials for hydrogen storage around the globe. MXenes are considered comparatively newer and more efficient 2D transition metal carbides/nitrides for hydrogen storage due to their astonishing properties including high surface area, tunable interlayer spacing, and thermal stability. Notably, the tuneable and amenable surface chemistry of MXenes plays a vital role in their hydrogen storage properties. In this study, hydrogen storage properties of multilayer Ti 3 C 2 T x MXenes are experimentally explored and investigated at 77 K for the first time. 2D Ti 3 C 2 T x MXenes sheets are synthesized via the etching method. Multilayer Ti 3 C 2 T x sheets are characterized by numerous physico-chemical techniques. The gravimetric hydrogen storage capacity of multilayer Ti 3 C 2 T x MXene is measured to be ∼10.47 wt% at 25 bar and 77 K, revealing an extraordinary hydrogen uptake in the multilayer MXene sample. To the best of the authors' knowledge, this is the first experimental report on the hydrogen storage performance of multilayer Ti 3 C 2 T x MXenes. This outstanding hydrogen storage uptake in 2D Ti 3 C 2 T x MXene may be a paradigm shift in the design and development of solid-state hydrogen storage technologies for portable and stationary power applications. It is hoped that the findings of this study would pique interest in more research in this area. Multilayer Ti 3 C 2 T x MXene shows ultrahigh gravimetric hydrogen storage capacity. These experimental findings may be a breakthrough in the development of solid-state hydrogen storage technology. [Display omitted] • H 2 as an energy carrier has immense potential to alleviate the world's growing energy crisis. • Multilayer Ti 3 C 2 T x MXene samples were engineered by the mild etching method. • Multilayer Ti 3 C 2 T x MXene exhibits an excellent gravimetric hydrogen storage capacity of ∼10.47 wt% at 77 K and 25 bar. • H 2 uptake capacity depends on the interlayer spacing and attached functional groups. [ABSTRACT FROM AUTHOR]

Transition metal carbides of group 5 (G5TMC=VC, NbC and TaC) with similar crystallite sizes were prepared by a sol-gel route. The catalysts were characterized and studied in the methanol steam reforming (MSR) reaction in the temperature range of 573–723 K at atmospheric pressure and using a stoichiometric CH 3 OH/H 2 O = 1/1 mole ratio mixture. Under the MSR reaction conditions used, the route of methanol transformation depends on the G5TMC used as catalyst. The catalytic behaviour of VC differs from that of NbC and TaC, which in turn show a similar behaviour. Over VC, methanol is mainly converted to a mixture of H 2 +CH 4 , whereas over NbC and TaC the major product obtained is HCHO, formed from the dehydrogenation of methanol. • Group 5 transition metal carbides as catalysts in the methanol steam reforming. • Methanol steam reforming over VC, NbC and TaC polycrystalline catalysts. • H 2 +CH 4 mixtures are obtained under MSR over VC catalyst. • HCHO is obtained under MSR over NbC and TaC catalysts. [ABSTRACT FROM AUTHOR]

Green hydrogen is seen as the fuel of the future as various efforts are made to further implement it in different industries and sectors. Green hydrogen offers a clean and emissions free renewable source of high energy density that helps work towards the global net zero emissions goal. Green hydrogen, which is produced via the hydrogen evolution reaction (HER), requires a technological breakthrough in the electrolyzer; the latter necessitates for the presence of non-precious, stable, and highly active electrocatalysts. Two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides (MXenes) are promising future electrocatalysts that have great reported exhibiting potential for commercial scalability due to their excellent intrinsic properties and structural flexibility. First, the synthesis methods are comprehensively summarized and discussed based on their electrocatalytic usage for the HER alongside their electronic properties. Second, this mini-review captures the current status of MXenes as electrocatalysts both experimentally and theoretically. The present MXenes can be separated into three categories: pristine, doped and hybrid structures where comparisons are drawn based on electrochemical descriptors backed by DFT studies. In addition, density functional theory (DFT) screening studies based on the Gibbs free energy of hydrogen adsorption are reported on different MXene variants. Pristine, double transition metal, carbonitride, vacancy induced, transition metal anchored and unique surface terminations MXenes are all reported, showing promising energetics for further experimental expansion in this field. Finally, secondary tools such as molecular dynamics and machine learning are coupled with DFT to explore novel MXene structures and efficiently predict their HER performance. • MXene as HER electrocatalysts are mainly synthesized via top-down methods. • Termination elements significantly impact HER kinetics of MXene electrocatalysts. • MXene heterostructures show lowest overpotentials and Tafel slopes. • HER DFT screening of pristine, carbonitride, double TM, and more MXenes. • MXene DFT exploration for HER is assisted with machine learning. [ABSTRACT FROM AUTHOR]

[Display omitted] • The development history of MXene and the advantage of combining with polymer membrane are reviewed. • Two basic preparation methods of MXenes (top-down and bottom-up) are briefly introduced. • The electronic properties, hydrophilicity, photothermal conversion, catalysis and antibacterial properties of MXene are discussed in points. • The applications of MXene in water treatment separation membrane, gas separation membrane, organic solvent separation membrane and ion exchange membrane are reviewed. • The future development direction and urgent problems of MXene-based polymer membranes are prospected. Transition metal carbides/nitrides/carbonitrides, commonly referred to as MXenes, have gained widespread attention since their discovery in 2011 as a promising family of two-dimensional (2D) materials. Their impressive chemical, electrical, thermal, mechanical, and biological properties have fueled a surge in research focused on the synthesis and application of MXenes in various fields, including membrane-based separation. By engineering the materials and membrane structures, MXene-based membranes have demonstrated remarkable separation performance and added functionalities, such as antifouling and photocatalytic properties. In this review, we aim to have a timely and critical review of research on their fabrication strategy and performance in advanced molecular separation and ion exchange, beginning with a brief introduction of the preparation and physicochemical properties of MXenes. Finally, outlooks and future works are outlined with the aims to provide valuable insights and guidance for advancing membranes' applications in different separation domains. [ABSTRACT FROM AUTHOR]

Compared with common monoanionic high entropy ceramics, polyanionic high entropy ceramics, with better performance, are more difficult to prepare. Since transition metal carbides have high hardness and transition metal nitrides have good toughness, it is hoped that high entropy carbonitride ceramics can combine the advantages of the two. In this paper, a series of novel (Ti 0.25 Nb 0.25 Hf 0.25 Ta 0.25)C x N 1–x (x = 0.3, 0.4, 0.5, 0.6, and 0.7) high entropy ceramics were successfully synthesized for the first time using spark plasma sintering at 1850 °C with metal carbides and metal nitrides as raw materials. The phase evolution, microstructure, hardness and fracture toughness of high carbonitride entropy ceramics were investigated. X-ray diffraction indicates the ceramics with the single-phase face-centered cubic structure were successfully prepared. It was found that the high entropy ceramics sintered at 1850 °C with four cationic components have excellent performance on fracture toughness (KIC = 7.1746 MPa m1/2). With the increase of carbide proportion, the hardness of the ceramics increased, but the fracture toughness and bending strength decreased slightly. And it was found that the differences of grain size and porosity content were the main reasons for the mechanical properties difference. The excellent hardness properties, good bending strength and outstanding fracture toughness of the high entropy ceramics provide the possibility for the application of high entropy ceramics in aerospace and other applications requiring high performance. [ABSTRACT FROM AUTHOR]

MXenes are electrically conductive 2D transition metal carbides/nitrides obtained by the etching of nanolaminated MAX phase compounds, followed by exfoliation to single‐ or few‐layered nanosheets. The mainstream chemical etching processes have evolved from pure hydrofluoric acid (HF) etching into the innovative "minimally intensive layer delamination" (MILD) route. Despite their current popularity and remarkable application potential, the scalability of MILD‐produced MXenes remains unproven, excluding MXenes from industrial applications. This work proposes a "next‐generation MILD" (NGMILD) synthesis protocol for phase‐pure, colloidally stable MXenes that withstand long periods of dry storage. NGMILD incorporates the synergistic effects of a secondary salt, a richer lithium (Li) environment, and iterative alcohol‐based washing to achieve high‐purity MXenes, while improving etching efficiency, intercalation, and shelf life. Moreover, NGMILD comprises a sulfuric acid (H2SO4) post‐treatment for the selective removal of the Li3AlF6 impurity that commonly persists in MILD‐produced MXenes. This work demonstrates the upscaled NGMILD synthesis of (50 g) phase‐pure Ti3C2Tz MXene clays with high extraction yields (>22%) of supernatant dispersions. Finally, NGMILD‐produced MXene clays dry‐stored for six months under ambient conditions experience minimal degradation, while retaining excellent redispersibility. Overall, the NGMILD protocol is a leap forward toward the industrial production of MXenes and their subsequent market deployment. [ABSTRACT FROM AUTHOR]

Reducing greenhouse gas emissions or collecting and converting existing greenhouse gases has become a global concern. One of the most effective methods of utilizing CH4 and CO2 resources is the dry reforming of methane (DRM). Transition metal carbide catalysts have attracted wide attention because of their excellent catalysis performance and carbon deposition resistance. However, pure-phase carbides are easily oxidized and deactivated at atmospheric pressure in DRM reactions. There is a problem of poor dispersion (Mo2C 17 m² /g). Therefore, this paper summarizes the effects of adding active sites and supported carbides on the DRM reaction, discusses the role of active sites and supports in the catalyst, and introduces the different preparation methods of transition metal carbides. This paper also reviews the catalyst mechanism of transition metal carbides in DRM reactions. Nevertheless, the current research in this field needs to be deepened. Therefore, it is necessary to strengthen the exploration of various catalyst preparation methods and mechanisms, so as to realize future improvement in this field. [ABSTRACT FROM AUTHOR]

Rechargeable metal‐ion batteries (MIBs) beyond lithium‐ion batteries based on Na, K, Mg, and Al metal electrodes which are earth‐abundant and low‐cost have been developed for large‐scale energy storage systems. MXenes, a type of transition metal carbides, nitrides, and carbonitrides, are discovered as electrodes for MIBs owing to their distinctive properties of large‐scale ultrathin conductive 2D structures, adjustable surface functional groups, regulable interlayer spacing, and high specific surface area. Herein, the properties of MXenes are summarized and the recent progress on MXene‐based materials for diversified MIBs (Li, Na, K, Mg, and Al‐ion batteries) is introduced. The main focus is on the synthesis and applications of MXene‐based materials in MIBs, and their roles in electrochemical reactions. Further examples are provided to demonstrate the significant function of MXene‐based composite as active materials, substrates, collectors, and precursors in different MIBs, highlighting the enormous potential of MXene‐based materials to construct advanced electrodes. This review expects to offer a deep understanding of the relationship between the electrochemical performance and the MXene‐based electrodes, which will promote more novel and creative breakthroughs in the MXenes‐based electrodes for MIBs. [ABSTRACT FROM AUTHOR]

Engineered 2D MXene-based materials for advanced supercapacitors and micro-supercapacitors. [Display omitted] The class of two-dimensional transition metal carbides/nitrides/oxycarbides (known as MXenes) has shown great potential in energy storage applications due to their intrinsic layered structure, outstanding electrical conductivity, tunable surface chemistry, and unique physicochemical properties. This review summarizes the latest progresses of MXene-based materials for supercapacitors and micro-supercapacitors. First, state-of-the-art structural engineering strategies for the construction of novel MXene-based electrodes are highlighted, as the electrochemical performance of MXenes is influenced by their structure, such as interlayer spacing and surface functional group density. Furthermore, the charge storage mechanisms of MXene-based electrodes in different electrolytes are discussed to stimulate further design and development of tailored materials for high-performance devices. Moreover, different device fabrication technologies are summarized and the achievements of specific device geometries (e.g. , fiber-shape, planar-type, and three-dimensional devices) containing MXene-based materials are critically reviewed. Finally, perspectives and outlook for the development of high-performance MXene-based electrodes in terms of material engineering, performance improvement and device innovation are provided, clearly indicating research directions for next-generation advanced energy storage devices. [ABSTRACT FROM AUTHOR]

MXenes, a family of 2D transition metal carbides, are considered promising high‐rate pseudocapacitive materials because of their metallic‐like conductivity and transition metal oxide‐like surfaces. Currently, nearly 50 stoichiometric MXenes have been synthesized. However, only a few MXenes, such as Ti3C2, have shown stable pseudocapacitive charge storage so far. Further improving the inherent pseudocapacitance of MXenes without losing their cyclability remains a challenge. Herein, a mild method is reported to produce highly stable bimetallic solid‐solution MXene Ti2VC2 using a solution of potassium fluoride and hydrochloric acid. The electrochemical properties of resulting multilayered clay‐like and delaminated Ti2VC2 films are investigated, exceeding the performance of typical Ti3C2 in acidic electrolytes. These electrodes deliver up to 2000 F cm−3 and retain more than 90% of their initial capacitance after 20 000 cycles, surpassing most state‐of‐the‐art supercapacitor materials known. The pseudocapacitive charge storage of Ti2VC2 is deeply investigated through in situ and ex situ experimental studies, confirmed the pseudocapacitive mechanism is a combination of hydrated H+ intercalation and surface redox. This work provides a practical route toward future rational design on the atomic scale for high‐performance pseudocapacitive materials. [ABSTRACT FROM AUTHOR]

The rational design of an active and stable electrocatalyst for the hydrogen evolution reaction (HER) is demonstrated as a major challenge for the renewable energy-driven water-splitting process. Herein, a unique structure of nitrogen-doped carbon-based Mo2C@TiO2 (NC/Mo2C@TiO2) was synthesized via controlling incorporation of TiO2 nanoparticles in the carbonization process to achieve promising electrocatalytic activity towards the HER. The electronic structure of Mo2C nanodots was regulated by TiO2 and nitrogen-doped carbon, thus exposing abundant active sites for the HER. Electrochemical measurement shows that the NC/Mo2C@TiO2 electrocatalyst has a low overpotential of 167 mV at 10 mA cm−2 with a Tafel slope of 158 mV dec−1 in 1 M KOH. The electrocatalyst shows excellent stability with a slightly declined current density of 92.88% after 35 h of operation because of the involvement of TiO2. Moreover, the design concept can be extended to developing other transition metal carbide electrocatalysts. [ABSTRACT FROM AUTHOR]

The soaring development of industry exacerbates the shortage of fresh water, making drinking water production an urgent demand. Membrane techniques feature the merits of high efficiency, low energy consumption, and easy operation, deemed as the most potential technology to purify water. Recently, a new type of two‐dimensional materials, MXenes as the transition metal carbides or nitrides in the shape of nanosheets, have attracted enormous interest in water purification due to their extraordinary properties such as adjustable hydrophilicity, easy processibility, antifouling resistance, mechanical strength, and light‐to‐heat transformation capability. In pioneering studies, MXene‐based membranes have been evaluated in the past decade for drinking water production including the separation of bacteria, dyes, salts, and heavy metals. This review focuses on the recent advancement of MXene‐based membranes for drinking water production. A brief introduction of MXenes is given first, followed by descriptions of their unique properties. Then, the preparation methods of MXene membranes are summarized. The various applications of MXene membranes in water treatment and the corresponding separation mechanisms are discussed in detail. Finally, the challenges and prospects of MXene membranes are presented with the hope to provide insightful guidance on the future design and fabrication of high‐performance MXene membranes. [ABSTRACT FROM AUTHOR]

Densifying transition metal carbide (TMC) ceramics is challenging due to their low diffusion coefficient and strong covalent bonding. Ultra-high-pressure sintering (UHPS) is a promising technique for preparing dense ceramic materials at low temperatures, but it is underutilized in TMC ceramics. Herein, we report the successful employment of UHPS at 1500 °C for 3 min with an auxiliary pressure of 7 GPa, yielding TaC, NbC, TiC, and ZrC ceramics with relative densities of 99.3%, 98.9%, 98.2%, and 96.4%, respectively. We demonstrate that the densification mechanism of the TMC ceramic in this investigation encompasses plastic deformation and high-pressure assisted atomic diffusion. Furthermore, we determine the Vickers hardness and fracture toughness of TaC, NbC, TiC, and ZrC ceramics to be 16.5, 15.9, 24.0, and 17.7 GPa and 2.5, 2.9, 2.8, and 1.8 MPa m1/2, respectively. Moreover, with increasing temperature from room temperature to 500 °C, the hardness and elastic modulus of all four TMC ceramics gradually decrease, with the hardness declining by approximately 17–25%. [ABSTRACT FROM AUTHOR]

In this work, we employ Density Functional Theory to study the effects of decoration with transition metal (TM) atoms—Ag, Au, Cu, Sc, Ti and Pd—on the H 2 adsorption properties of tin carbide monolayers (SnC-ML), as a prospective material for hydrogen storage. The results indicate that TM adatoms are strongly bonded to the SnC-ML and that electronic charge is transferred from the adatoms to the SnC-ML. In particular, it is found that Sc and Ti are chemisorbed on SnC-ML with strong binding energies. The most stable adsorption site for these metal atoms is above Sn atoms of the SnC-ML. Also, these TM atoms exhibit the higher hydrogen-storage capacities with up to four hydrogen molecules per adatom. In contrast, the other studied metals have at most 2 hydrogen molecules adsorbed. Approximate temperature- and pressure-dependent curves suggest that, to storage hydrogen, Sc- and Ti-decorated SnC-ML should be cooled under freezing temperatures, or kept at 1 MPa and 2.5 MPa, respectively, which are much lower pressures than those currently used in vehicular tanks, which attain pressures of 35 MPa. These results indicate that Sc and Ti decorated SnC-ML can be useful as hydrogen-storage solid-state devices. [Display omitted] • SnC monolayers with transition metal adatoms have been investigated as hydrogen-storage materials. • Sc and Ti atoms are strongly bonded to the carbon atom of the SnC monolayers. • SnC monolayers with Sc and Ti atoms have a high capacity for hydrogen storage. • SnC monolayers with Ag and Au atoms have poor hydrogen storage capacities. • H 2 is physisorbed on transition metal-decorated SnC monolayers. [ABSTRACT FROM AUTHOR]

The catalytic de/hydrogenation process is important in the fields of petrochemical refining, fuel synthesis, drug synthesis, CO2 conversion, and hydrogen synthesis, where the construction of low‐cost and high‐efficiency de/hydrogenation catalysts attracting significant attentions. Molybdenum carbide (MoxC), as a non‐noble transition metal carbide catalyst, has been widely investigated for hydrogen activation. Herein, research progress and achievements of molybdenum carbide for catalytic de/hydrogenation are reviewed. Additional attention is paid to the structure and crystal phase of molybdenum carbide, and various modification strategies related to the catalytic activity regulation are summarized. Finally, the application prospect of molybdenum carbide catalysts is also discussed. This review provides a framework reference for further understanding the design and utilization of molybdenum carbide catalysts for catalytic de/hydrogenation and the key research problems to be addressed. [ABSTRACT FROM AUTHOR]

Advancement in the field of nanoscience and nanotechnology has envisaged the development of novel materials for a better human life. Nanomaterials have attracted the scientific research for the past three decades and are widely explored for multifunctional applications. Research is ongoing to understand the properties of various emerging nanomaterials such as MXenes, MBenes, transition metal dichalcogenides, black phosphorous, and so forth to name a few. Among the various layered two‐dimensional (2D) materials, transition metal carbides/nitrides/carbonitrides (collectively known as MXenes) have received profound interest due to their exciting physical and chemical properties. Among the MXene family, titanium‐based MXenes have been explored the most. But the research on non‐titanium‐based MXenes are still in the developing stage. Zirconium (Zr)‐based MXenes are the emerging materials having peculiar characteristics. Herein, we discuss the syntheses, properties, and application of Zr‐based MXenes. Initially, the MAX phases of Zr‐based MXenes are discussed. Further, the synthesis of Zr‐based MXenes by various methods are included. Furthermore, the applications of Zr‐based MXenes in rechargeable batteries such as lithium‐ion batteries, sodium‐ion batteries, potassium‐ion batteries, and so forth are reviewed. [ABSTRACT FROM AUTHOR]

This study investigated the high-temperature oxidation behaviors of TMC ceramics. The results indicate that the high-temperature oxidation curves of the four TMC ceramics follow a parabolic law, suggesting a diffusion-controlled process. The activation energies for the oxidation of TaC, NbC, TiC, and ZrC ceramics are 105.4, 124.3, 169.3, and 78.7 kJ/mol, respectively, with oxidation rate constants at 1000 °C of 16.84, 40.45, 0.18, and 14.43 mg2/cm4·h for each ceramic, respectively. The temperatures at which the ceramics disintegrate into fragments in high-temperature air are 800, 800, >1000, and 600 °C, respectively. The anti-oxidation performance of the four TMC ceramics ranks as follows: TiC > TaC > NbC > ZrC. In comparison to the reported high-entropy carbide ceramics, the TiC ceramic in this study demonstrates superior anti-oxidation performance due to dense TiO 2 layer formation, characterized by significantly low oxidation rates and excellent structural stability. [ABSTRACT FROM AUTHOR]

Transition metal carbides have emerged as an attractive alternative to conventional catalysts in hydrodeoxygenation (HDO) reactions due to surface reactivity, catalytic activity, and thermodynamic stability similar to those of noble metals. In this study, the impact of varying Mo concentration in carbon nanofiber-supported catalysts for the supercritical ethanol-assisted HDO of bio-oils in an autoclave batch reactor is discussed. Raw bio-oils derived from agave bagasse and corncob through solar hydrothermal liquefaction were treated at 350 °C. Our findings indicate that the presence of Mo has a strong impact on both product yield and chemical properties. Thus, a Mo concentration of 10 wt.% is enough to obtain high deoxygenation values (69–72%), resulting in a yield of upgraded bio-oil ranging between 49.9 and 60.4%, depending on the feedstock used, with an energy content of around 35 MJ/kg. A further increase in the Mo loadings (20 and 30 wt.%) reduced the loss of carbon due to gasification and improved the bio-oil yields up to 62.6 and 67.4%, without compromising the product quality. [ABSTRACT FROM AUTHOR]

This study focuses on the utilization of two‐dimensional Ti3C2 MXene as a catalyst for photocatalytic hydrogen production. MXenes, a class of transition metal carbides/nitrides, exhibit exceptional properties conducive to enhancing photocatalytic reactions. This research explores the performance of Ti3C2 MXene as a cocatalyst in photocatalytic systems, aiming to improve charge separation, inhibit recombination, and facilitate efficient hydrogen evolution from water under light irradiation. The synthesis methods, catalyst‐loading strategies, and overall photocatalytic mechanisms are investigated, shedding light on the potential of Ti3C2 MXene as a promising material for advancing hydrogen production through sustainable means. [ABSTRACT FROM AUTHOR]

Highlights: An ultralight and flexible supercapacitor is developed by an effective 3D fabrication method that uses MXene to fabricate waste denim felt through needling and carbonization. The electrodes have a maximum specific capacitance of 1748.5 mF cm−2 and demonstrate remarkable cycling stability with more than 94% after 15,000 galvanostatic charge/discharge cycles The loaded more MXene onto Z-directional fiber bundles results in enhanced specific capacitance, energy density and power density of supercapacitors. MXene, a transition metal carbide/nitride, has been prominent as an ideal electrochemical active material for supercapacitors. However, the low MXene load limits its practical applications. As environmental concerns and sustainable development become more widely recognized, it is necessary to explore a greener and cleaner technology to recycle textile by-products such as cotton. The present study proposes an effective 3D fabrication method that uses MXene to fabricate waste denim felt into ultralight and flexible supercapacitors through needling and carbonization. The 3D structure provided more sites for loading MXene onto Z-directional fiber bundles, resulting in more efficient ion exchange between the electrolyte and electrodes. Furthermore, the carbonization process removed the specific adverse groups in MXenes, further improving the specific capacitance, energy density, power density and electrical conductivity of supercapacitors. The electrodes achieve a maximum specific capacitance of 1748.5 mF cm−2 and demonstrate remarkable cycling stability maintaining more than 94% after 15,000 galvanostatic charge/discharge cycles. Besides, the obtained supercapacitors present a maximum specific capacitance of 577.5 mF cm−2, energy density of 80.2 μWh cm−2 and power density of 3 mW cm−2, respectively. The resulting supercapacitors can be used to develop smart wearable power devices such as smartwatches, laying the foundation for a novel strategy of utilizing waste cotton in a high-quality manner. [ABSTRACT FROM AUTHOR]

The two-dimensional structures of transition metal nitride and carbide, TiN, and TiC have been alloyed with lithium (Li) in replacement of Ti, and their Li-ion applicability has been investigated using density functional theory and general gradient approximation. The alloy composition of x = 0.125 , 0.25, 0.375, and 0.5 have been considered and the stability of the alloys has been proved by cohesive energy and phonon density of states results. Moreover, the bond lengths between atoms as structural properties have been studied for these alloy structures. The largest peak of quantum capacitance and the largest negative value of surface storage charge are for alloy composition of TiC with x = 0.125 with the values of 909.79 μ F/cm 2 and - 1819.58 μ C/cm 2 , respectively. Moreover, the results of the quantum capacitance and surface storage charge as a function of voltage for all Li alloy compounds are in the range of excellent supercapacitors and could have good potential to use as an electrode in the capacitor of Li-ion batteries. Furthermore, the electronic density of states of this group of alloys represents metallic behavior and therefore electrode material. In addition, the diffusion coefficient at temperatures of 77 and 300 K has been calculated using molecular dynamic calculations, and its lowest and largest values are 8 × 10 - 8 cm 2 /s (at 77 K) and 5.6 × 10 - 7 cm 2 /s (at 300), respectively. Plus, the largest value of electrical conductivity per relaxation time at 300 K belongs to Li 0.25 Ti 0.75 C with a value of 9.8 × 10 19 /(Ω m s). [ABSTRACT FROM AUTHOR]

The typical semi conductivity and few active sites of hydrogen evolution of 2H MoSe2 severely restrict its electrocatalytic hydrogen evolution performance. At the same time, the 1T MoSe2 has metal conductivity and plentiful hydrogen evolution sites, making it feasible to optimize the electrocatalytic hydrogen evolution behavior of MoSe2 using phase engineering. In this study, we, through a simple one-step hydrothermal method, composed 1T/2H MoSe2, and then used newly emerging transition metal carbides with several atomic-layer thicknesses Ti3C2Tx to improve the conductivity of a MoSe2-based electrocatalyst. Finally, MoSe2@Ti3C2Tx was successfully synthesized, according to the control of the additional amount of Ti3C2Tx, to form a proper MoSe2/ Ti3C2Tx heterostructure with a better electrochemical HER performance. As obtained MoSe2@4 mg-Ti3C2Tx achieved a low overpotential, a small Tafel slope and this work offers additional insight into broadened MoSe2 and MXenes-based catalyst's electrochemical application. [ABSTRACT FROM AUTHOR]