Transition Metal Nitrides Research Articles

Effect of vacancy, doping and alloying on supercapacitance properties of monolayer CrN/CuN heterostructure as an electrode material: A first principle study

In this paper, the supercapacitance applicability of monolayer CrN/CuN heterostructure as a transition metal nitride interface is studied using density functional theory. Moreover, the vacancies, doped, and alloys of this heterostructure are investigated, and their mechanical and structural stabilities are confirmed. In addition, the quantum capacitance and surface charge storage as a function of applied voltage have been calculated. The largest peak of quantum capacitance belongs to the single-side alloy of CrN/VCuN (V atoms in replacement of Cu atoms) with a value of 405.64 μF/cm2 at -0.005 V which suggests an excellent candidate of cathode material for supercapacitance applications. Furthermore, the largest value of the surface charge storage is related to the doped heterostructure of HfCrCN/VCuPN (Hf and C atoms in replacement of Cr and N atoms, V and P atoms in replacement of Cu and N atoms) with a value of -236.27 μC/cm2 at −1 V.

Regulation of electrons between Ru and VN for high performance HER of low-level Ru doping in vanadium-nitrogen doped carbon catalysts

Transition metal nitrides (TMNs) have garnered significant attention for their catalytic activity similar to noble metals, attributed to their distinctive electronic structures. However, the sluggish reaction kinetics have hindered the progress in TMN development. In this study, an alloying approach was employed to create Ru@VN/C catalysts by uniformly dispersing low levels of ruthenium (Ru) in vanadium-nitrogen doped carbon (VN/C) on carbon spheres. Through alloying, the electronic structures of ruthenium and vanadium atoms were further adjusted, leading to exceptional catalytic activity resulting from unique electron transfer between the atoms. The Ru@VN/C catalyst demonstrated a low overpotential of 5 mV and a Tafel slope of 27 mV·dec−1 at 10 mA·cm−2 in alkaline seawater solution, as well as superior performance in alkaline and simulated seawater solutions. The interatomic synergistic interactions, driven by charge redistribution as confirmed by density functional theory calculations and experimental data, play a crucial role in expanding the applications of TMNs in green hydrogen production.

Synergistic effect of co-sputtered tungsten-titanium nitride as electrode material for efficient hybrid supercapacitors

The dawn of bimetallic transition metal nitrides has attracted considerable interest as battery grade electrode material for potential energy storage applications. In addition, it is essential to investigate binder-free processes to improve the performance of the fabricated electrodes. In this study, binder-free tungsten‑titanium nitrides (W-TiN) are deposited through RF/DC magnetron co-sputtering onto the conducting nickel foam (NF). SEM, EDX and X-ray diffraction are exploited to investigate surface morphology, elemental composition, and structural properties of sputtered materials. The W-TiN electrodes are characterized through electrochemical investigation in half-cell configuration. The tested W-TiN electrode is further utilized with activated carbon (AC) electrode to develop hybrid supercapacitor device W-TiN//AC. The hybrid device revealed a maximum energy density (Es) of 88.8 Wh/kg and power density (Ps) 1700 W /kg. To further understand the mechanism of hybrid devices, the capacitive and diffusive contributions are computed using linear and quadradic models. This study provides a new direction to integrate co-sputtered binder-free electrode materials and devices for large scale production of advanced hybrid energy storage devices.

Recent progress in MXenes-based lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are considered as the potent candidates for next-generation energy storage systems due to their high theoretical energy density. However, some inherent problems, including sulfur insulation, shuttle effect caused by lithium polysulfides, and lithium dendrites, hinder their practical application. Various materials have been studied to address the aforementioned issues. A class of two-dimensional inorganic compounds (MXenes), such as transition metal carbides, nitrides, and carbon nitrides, have recently emerged. In this review, we summarize the characteristics and commonly used preparation methods of MXenes and outline the latest development of MXenes and their composites in LSBs. When utilized as sulfur carriers, modified layers of separators, hosts for lithium metal anodes, and electrolyte additives in LSBs, the diversity of structure, excellent conductivity, and high mechanical strength of MXenes and their composites highlight the competitive advantages. This review provides some ideas for the future development of MXenes in LSBs.

Momentum-Resolved Electronic Structures and Strong Electronic Correlations in Graphene-like Nitride Superconductors.

Although transition-metal nitrides have been widely applied for several decades, experimental investigations of their high-resolution electronic band structures are rare due to the lack of high-quality single-crystalline samples. Here, we report on the first momentum-resolved electronic band structures of titanium nitride (TiN) films, which are remarkable nitride superconductors. The measurements of the crystal structures and electrical transport properties confirmed the high quality of these films. More importantly, from a combination of high-resolution angle-resolved photoelectron spectroscopy and first-principles calculations, the extracted Coulomb interaction strength of TiN films can be as large as 8.5 eV, whereas resonant photoemission spectroscopy yields a value of 6.26 eV. These large values of Coulomb interaction strength indicate that superconducting TiN is a strongly correlated system. Our results uncover the unexpected electronic correlations in transition-metal nitrides, potentially providing a perspective not only to understand their emergent quantum states but also to develop their applications in quantum devices.

Solvent-free one-step green synthesis of MXenes by “gas-phase selective etching”

Two-dimensional transition metal carbides and nitrides (MXenes) have attracted extensive attention due to their unique electronic properties and various applications for energy harvesting. However, the current synthesis procedures involve using fluoride-based aqueous solutions via reacting with Al-containing MAX phases. Besides, fluorine-free, cost-effective, and straightforward synthetic methods are rarely reported and need to be explored. Here, a solvent-free one-step gas-phase dry etching method, named “Gas-Phase Selective Etching”, was first proposed and used to etch different elements A (Al, Si, Sn, etc.) of MAX phases using the strong oxidation ability of halogens and hydrogen halides gases (Cl2, Br2, I2, HCl, HBr, and HI). The gas-phase etching can achieve a pure product of MXenes coupled with specific gas-induced functional groups. Meanwhile, MXenes powder can be directly obtained without the removal processes of etchants and by-products. Furthermore, the multilayer-MXene with -Cl functional groups (Ti3C2Cl2) has strong oxidation resistance and superior rate performance of capacitance. It provides us with an intelligent, cost-effective synthesis strategy that has a high yield and is safe, allowing for the promising mass production of MXenes.

Facilitating Atom Probe Tomography of 2D MXene Films by In Situ Sputtering.

2D materials are emerging as promising nanomaterials for applications in energy storage and catalysis. In the wet chemical synthesis of MXenes, these 2D transition metal carbides and nitrides are terminated with a variety of functional groups, and cations such as Li+ are often used to intercalate into the structure to obtain exfoliated nanosheets. Given the various elements involved in their synthesis, it is crucial to determine the detailed chemical composition of the final product, in order to better assess and understand the relationships between composition and properties of these materials. To facilitate atom probe tomography analysis of these materials, a revised specimen preparation method is presented in this study. A colloidal Ti3C2Tz MXene solution was processed into an additive-free free-standing film and specimens were prepared using a dual beam scanning electron microscope/focused ion beam. To mechanically stabilize the fragile specimens, they were coated using an in situ sputtering technique. As various 2D material inks can be processed into such free-standing films, the presented approach is pivotal for enabling atom probe analysis of other 2D materials.

Molybdenum nitride thin films coated cobalt-metal-organic framework nanocolumns for high-efficiency alkaline hydrogen evolution

The sustainable development of catalysts with Pt-like catalytic activity to produce hydrogen economically from water electrolysis is essential and challenging. Herein, we have prepared a novel catalyst with the combined virtues of nanocolumn structures and heterojunctions by magnetron sputtering molybdenum nitride (Mo2N) thin films over cobalt-metal-organic framework (Co-MOF) nanocolumns on carbon paper (CP), and explored the catalytic activities in hydrogen evolution reaction (HER). By optimizing the preparation process, the heterostructured Co-MOF@Mo2N/CP catalysts can exhibit an excellent HER performance with an overpotential of only 72.8 mV at 10 mA cm−2 and cycling durability over 24 h and 5000 cycles, achieving one of the best performances among state-of-the-art Mo-based catalysts. This work guides and accelerates the design of low-cost and high-performance transition metal nitrides HER catalysts for industrial applications.

Lightweight and robust cellulose/MXene/polyurethane composite aerogels as personal protective wearable devices for electromagnetic interference shielding

The increasing electromagnetic pollution is urgently needed as an electromagnetic interference shielding protection device for wearable devices. Two-dimensional transition metal carbides and nitrides (MXene), due to their interesting layered structure and high electrical conductivity, are ideal candidates for constructing efficient conductive networks in electromagnetic interference shielding materials. In this work, lightweight and robust cellulose/MXene/polyurethane composite aerogels were prepared by mixing cellulose nanofiber (CNF) suspensions with MXene, followed by freeze-drying and coating with polyurethane. In this process, CNF effectively assembled MXene nanosheets into a conductive network by enhancing the interactions between MXene nanosheets. The prepared aerogel exhibited the shielding effectiveness of 48.59 dB in the X-band and an electrical conductivity of 0.34 S·cm−1. Meanwhile, the composite aerogel also possessed excellent thermal insulation, infrared stealth, mechanical and hydrophobic properties, and can be used as a wearable protective device to protect the human body from injuries in different scenarios while providing electromagnetic interference shielding protection.

Robust Ferromagnetism in Hexagonal Honeycomb Transition Metal Nitride Monolayer.

Two-dimensional intrinsic magnetic materials with high Curie temperature are promising candidates for next-generation spintronic devices. In this work, we design two kinds of two-dimensional transition metal nitrides, VN2 and FeN2, both with a hexagonal honeycomb lattice. Based on the formation energy, and phonon spectra calculations as well as the molecular dynamics simulations, their structural stability is demonstrated. Then, we determine the ferromagnetic ground states of VN2 and FeN2 monolayers through the energy calculations, and the Curie temperatures of 222 K and 238 K are estimated by solving the Heisenberg model using the Monte Carlo simulation method. Hence, the VN2 and FeN2 monolayers are demonstrated to be new two-dimensional ferromagnetic materials with high temperature ferromagnetism or large-gap half-metallicity.

Recent Advancements in Ascribing Several Platinum Free Electrocatalysts Pertinent to Hydrogen Evolution from Water Reduction.

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.

General synthesis of transition metal nitride arrays by ultrafast flash joule heating within 500 ms

General synthesis of transition metal nitride arrays by ultrafast flash joule heating within 500 ms

One‐step Synthesis of Organic Terminal 2D Ti3C2Tx MXene Nanosheets by Etching of Ti3AlC2 in an Organic Lewis Acid Solvent

AbstractThe surface and interface chemistry are critical for controlling the properties of two‐dimensional transition metal carbides and nitrides (MXenes). Numerous efforts have been devoted to the functionalization of MXenes with small inorganic ligands; however, few etching methods have been reported on the direct bonding of organic groups to MXene surfaces. In this work, we demonstrated an efficient and rapid strategy for the direct synthesis of 2D Ti3C2Tx MXene nanosheets with organic terminal groups in an organic Lewis acid (trifluoromethanesulfonic acid) solvent, without introducing additional intercalations. The dissolution of aluminum and the subsequent in situ introduction of trifluoromethanesulfonic acid resulted in the extraction of Ti3C2Tx MXene (T=CF3SO3−) (denoted as CF3SO3H−Ti3C2Tx) flakes with sizes reaching 15 μm and high productivity (over 70 %) of monolayers or few layers. More importantly, the large CF3SO3H−Ti3C2Tx MXene nanosheets had high colloidal stability, making them promising as efficient electrocatalysts for the hydrogen evolution reaction.

One-step Synthesis of Organic Terminal 2D Ti3C2Tx MXene Nanosheets by Etching of Ti3AlC2 in an Organic Lewis Acid Solvent.

The surface and interface chemistry are critical for controlling the properties of two-dimensional transition metal carbides and nitrides (MXenes). Numerous efforts have been devoted to the functionalization of MXenes with small inorganic ligands; however, few etching methods have been reported on the direct bonding of organic groups to MXene surfaces. In this work, we demonstrated an efficient and rapid strategy for the direct synthesis of 2D Ti3C2Tx MXene nanosheets with organic terminal groups in an organic Lewis acid (trifluoromethanesulfonic acid) solvent, without introducing additional intercalations. The dissolution of aluminum and the subsequent in situ introduction of trifluoromethanesulfonic acid resulted in the extraction of Ti3C2Tx MXene (T=CF3SO3 -) (denoted as CF3SO3H-Ti3C2Tx) flakes with sizes reaching 15 μm and high productivity (over 70 %) of monolayers or few layers. More importantly, the large CF3SO3H-Ti3C2Tx MXene nanosheets had high colloidal stability, making them promising as efficient electrocatalysts for the hydrogen evolution reaction.

Effect of oxygen substitution and oxycarbide formation on oxidation of Ti3AlC2 MAX phase

AbstractMAX phases, ternary transition metal carbides and nitrides, represent one of the largest families of layered materials. They also serve as precursors to MXenes, two‐dimensional (2D) carbides and nitrides. The possibility of oxygen substitution in the carbon sublattice, forming oxycarbide MAX phases and MXenes, was recently reported using secondary ion mass spectrometry. However, while the effect of oxygen substitution on the properties of MXenes was investigated, little is known about its effect on the properties of MAX phases. Here, we explore the influence of process parameters (e.g., particle size, synthesis temperature, annealing time, etc.) and oxygen presence in the lattice on the oxidation resistance of Ti3AlC2 MAX phase powders. We show that X‐ray diffraction measurements can identify oxygen substitution and assist in selecting MAX precursors to synthesize stable and highly conductive MXenes. Eliminating the substitutional oxygen from the MAX phase lattice increases the onset of oxidation by 400°C, from approximately 490 to 890°C. Finally, we discuss the impact of oxygen substitution in the MAX phases on the synthesis of MXenes and their resulting properties.

An Alternative Immune Cell Labeling System Based on the New Two-Dimensional Nanomaterials MXenes

Abstract Deepening our understanding of immune cell behavior is vital for creating safe, effective treatments, particularly as immune cell therapy, also known as cellular immunotherapy or cell-based immunotherapy, represents a groundbreaking approach in the treatment of various diseases, including cancer. Transition metal carbides and nitrides (MXenes), a novel family of 2D nanomaterials, show promise as advanced trackers for immune cells—key for precise diagnostics and therapies. Traditional cell labeling methods have stagnated due to limited chemical options, impeding progress in applied medicine. Moreover, these methods are incompatible with single-cell mass cytometry by time-of-flight (CyTOF), a globally adopted technology that improves classical flow cytometry. We propose an innovative solution utilizing MXenes to overcome these challenges. Our method, Label-free sINgle-cell tracKing of 2D matErials by mass cytometry (LINKED), leverages a novel, biocompatible, multiplexed, label-free detection approach via CyTOF and Mass Ion Beam Imaging by Time-of-Flight (MIBI-TOF). This technique overcomes chemical limitations and integrates seamlessly with CyTOF, allowing for nanomaterial detection and simultaneous measurement of diverse immune cell and tissue features. Our work promises to advance immunological research significantly, offering refined cell labeling and tracking techniques crucial for the advancement of translational medicine.

Exploring the Biomedical Potential of MXenes in Macrophage Phenotype Identification and Tracking

Abstract Macrophages are innate immune cells with varying phenotypes and functions that are influenced by their microenvironment. The distinction between the classical M1 and M2 phenotypes has been crucial in understanding their involvement in inflammation. Recently single-cell technologies have revealed a complex range of macrophage activation states, each contributing differently to maintaining physiological balance and affecting the development and progression of diseases. Identifying the origins and function of these macrophage subsets remains a complex challenge. MXenes, a category of two-dimensional transition metal carbides and nitrides, show promise in the biomedical field owing to their notable features, such as biocompatibility. MXenes' unique chemical properties allow for their detection at the single-cell and tissue level using mass cytometry (CyTOF), which shows great promise for biomedical applications. We found that MXenes can be internalized by myeloid cell precursors, monocytes, and macrophages without affecting their survival or differentiation. Early evaluations of MXenes uptake by immune cells have shown their detectability even after 30 minutes of incubation, attributable to their chemistry and impressive signal-to-noise ratio at CyTOF. These characteristics position MXenes as effective tools for precise single-cell labeling and in vivo monitoring of monocyte-derived macrophage phenotypes across various tissues and in response to specific stimuli or diseases.

Mechanical properties of hafnium tantalum carbides via field assisted sintering technology for hypersonic vehicles

Ultra-high temperature ceramics (UHTCs) are refractory transition-metal carbides, nitrides, and borides with the highest melting temperatures known materials, making them prime candidates for applications in aerospace and hypersonic vehicles. Of the UHTCs, tantalum carbide (TaC) and hafnium carbide (HfC) feature the highest melting temperatures. We investigated the binderless consolidation of HfC/TaC powder blends using Field Assisted Sintering Technology (FAST). Powders consisting of 90/10, 50/50, and 10/90 vol% HfC:TaC were sintered to high densities (>94 %). Bulk and nanomechanical, chemical, and microstructural characterization revealed substantially greater strength, hardness, and stiffness for ternary alloys. Mechanical properties correlated with physiochemical analysis indicated trace oxygen phases, solid-solution strengthening, and nonstoichiometric carbon were the key mechanisms driving the peak property enhancement of the 50 vol% solid-solution sample, despite lower densities. This study provides insight into optimizing the compositional design of HfC-TaC alloys by balancing influences from solid solution strengthening and the thermodynamic effects of oxygen/carbon stoichiometry.

Fabrication strategies, applications and prospects of MXene titanium nitride (Tin+1NnTx): A mini review

MXenes, as promising two-dimensional (2D) transition metal carbides or nitrides, are a promising new family of 2D materials. MXenes have superior electrical conductivity, a unique accordion-like structure, excellent mechanical properties and abundant surface termination, which make them the preferred material for the ever-growing market of energy storage, adsorption, gas sensing and other fields. As one of the typical representatives of the MXene family, Tin+1NnTx MXene is notable due to its high conductivity, high specific capacitance, high catalytic activity and low precursor cost compared to other MXenes and can be used for clean energy storage and catalysis applications. However, relatively little is currently known about the MXene Tin+1NnTx, and a special review on the synthesis, properties, and applications of Tin+1NnTx has not been reported to date. Herein, we overview and introduce the synthesis progress, application and properties of MXene Tin+1NnTx. The major problems and bottlenecks are objectively dissected and evaluated. In addition, future viewpoints and research opportunities are presented for the development of advanced MXene and MXene-based materials.

Controllable boosting activity on Co4N by Fe substitution for oxygen evolution reaction and efficient 5-hydroxymethylfurfural oxidation

The design of transition metal nitrides with excellent oxygen evolution reaction and 5-hydroxymethylfurfural oxidation reaction (HMFOR) is of great significance to achieve the goal of "carbon peaking and carbon neutrality". Herein, Fe-doped bimetallic nitride FexCo1-x)4N was prepared by a simple electron regulation strategy. The introduction of Fe changes the electronic structure of Co and optimizes the adsorption energies of *OH, reduces the potential barrier for the generation of *OOH as a potential-determining step and thus increases the intrinsic OER activity of Co4N. In addition, Fe substitution of some of the Co atoms gives (FexCo1-x)4N a higher electrochemical active surface area, which accelerates the electron transfer efficiency and improves the electrical conductivity. The overpotential for (FexCo1-x)4N-0.9 to reach a current density of 10 mA cm−2 in 1 M KOH is only 271 mV. When in 1 M KOH + 50 mM HMF condition, (FexCo1-x)4N-0.9 requires only 1.37 V to reach a current density of 10 mA cm−2. This work provides practical guidance for developing bifunctional transition metal electrocatalysts with excellent OER and HMFOR activity.