Metal Carbides Research Articles

Research progress in transition metal carbides in electrocatalytic hydrogen evolution reaction

Research progress in transition metal carbides in electrocatalytic hydrogen evolution reaction

Functionalization of Ti3C2 MXene with Diethylenetriamine for a Column-Based Solid-Phase Extraction of Heavy Metals.

Transition metal carbides, nitrides, and carbonitrides, known as MXenes, are attracting attention for their potential application in trace detection of heavy metals. This study presents diethylenetriamine-functionalized Ti3C2 MXene for trace detection of cadmium and lead ions. Functionalization of Ti3C2 significantly improves the adsorption properties of MXenes by replacing native functional groups with silane moieties that contain three amine groups, offering higher affinity for heavy metals. We demonstrate the efficacy of this material as a solid-phase extractor in column-based solid-phase extraction for heavy metal analysis in various food samples. Diethylenetriamine-functionalized Ti3C2 coupled with the flame atomic absorption spectrometer exhibits exceptional analytical performance. While maintaining a robust stability for 15 adsorption-desorption cycles, the proposed method shows detection limits of 0.09 ng mL-1 for cadmium and 1.7 ng mL-1 for lead, with a linear dynamic range of 0.3-50 ng mL-1 for cadmium and 5-90 ng mL-1 for lead, and relative recoveries of 97.50-101.05 and 98.65-100.80% for cadmium and lead ions, respectively. Additionally, relative standard deviations and enrichment factors were calculated as 0.60-4.70% and 42.3 for cadmium ions and 0.65-1.24% and 44.2 for lead ions.

Measuring the Surface Energy of Nanosheets by Emulsion Inversion.

Solution-processed nanomaterials can be assembled by a range of interfacial techniques, including as stabilizers in Pickering emulsions. Two-dimensional (2D) materials present a promising route toward nanosheet-stabilized emulsions for functional segregated networks, while also facilitating surface energy studies. Here, we demonstrate emulsions stabilized by the 2D materials including the transition metal carbide MXene, titanium carbide (Ti3C2T x ), and develop an approach for in situ measurement of nanosheet surface energy based on emulsion inversion. This approach is applied to determine the influence of pH and nanosheet size on surface energy for MXene, graphene oxide, pristine graphene, and molybdenum disulfide. The surface energy values of hydrophilic Ti3C2T x and graphene oxide decrease significantly upon protonation of usually dissociated functional groups, facilitating emulsion stabilization. Similarly, pristine graphene and molybdenum disulfide increase in surface energy when their surface functional groups are deprotonated under basic conditions. In addition, the surface energies of these pristine materials are correlated with nanosheet size, which allows for the calculation of the basal plane and edge surface energies of pristine nanosheets. This understanding of surface energies and control of emulsion inversion will allow design of emulsion-templated structures and surface energy studies of a wide range of solution-processable nanomaterials.

Exploring the thermal and optical characteristics of Ti3C2 MXene for enhanced photothermal conversion

Ti3C2 MXene, a member of the two-dimensional (2D) transition metal carbides family, has garnered significant attention for its exceptional photothermal properties. To understand the mechanistic underpinnings of this feature, we conducted a comprehensive first-principles density functional theory analysis. This study was aimed at investigating the electronic band structure and vibrational characteristics of Ti3C2 MXene to unravel its microscopic process of photothermal conversion. After obtaining its optical and thermal properties, the process by which the material moves from light absorption to heat release is elucidated. The presence of localized surface plasmon resonance (LSPR) effects in Ti3C2 is proved by Finite-difference time-domain (FDTD) simulations. The synergy between the high thermal conductivity network in the Ti layers and the LSPR phenomenon is believed to be responsible for the superior photothermal conversion capabilities. This investigation enhances the understanding of the intrinsic properties of Ti3C2 MXene, confirming its status as an ultrahigh photothermal conversion material.

Precharge switch based on metal–oxide–semiconductor‐controlled thyristor for power relay assembly of battery electric vehicles

AbstractThe power relay assembly (PRA) is an essential component to ensure the safety of an electric vehicle. We propose a semiconductor‐based precharge switch to overcome the shortcomings of the conventional mechanical relay, which is currently used as the precharge switch in the PRA. The gate‐driving circuit uses a photocoupler instead of a gate‐driving integrated circuit to reduce complexity and cost. Five devices, namely, two insulated‐gate bipolar transistors (IGBTs), two silicon carbide metal–oxide–semiconductor field‐effect transistors (SiC MOSFETs), and one metal–oxide–semiconductor‐controlled thyristor (MCT) are tested as candidate precharge switches. Each device is analyzed under varying battery voltage and fixed measurement conditions. The IGBT and SiC MOSFET burn below 600 V, while the MCT exhibits normal operation up to 800 V. The MCT precharge switch can solve shortcomings of the conventional mechanical relay and increase the performance with a simple gate‐driving circuit. Furthermore, the PRA with an MCT precharge switch can reduce the volume, weight, and cost while improving reliability.

A simple Urea approach to N-doped α-Mo2C with enhanced superconductivity

Abstract Chemical doping is a critical factor in the development of new superconductors or optimizing the superconducting transition temperature (T c) of the parent superconducting materials. Herein, a new simple urea approach is developed to synthesize the N-doped α-Mo2C. Benefiting from the simple urea method, a broad superconducting dome is found in the Mo2C1-x N x (0 ≤ x ≤ 0.49) compositions. XRD results show that the structure of α-Mo2C remains unchanged and that there is a variation of lattice parameters with nitrogen doping. Resistivity, magnetic susceptibility, and heat capacity measurement results confirm that the superconducting transition temperature (T c) was strongly increased from 2.68 K (x = 0) to 7.05 K (x = 0.49). First-principles calculations and our analysis indicate that increasing nitrogen doping leads to a rise in the density of states at the Fermi level and doping-induced phonon softening, which enhances electron-phonon coupling. This results in an increase in T c and a sharp rise in the upper critical field. Our findings provide a promising strategy for fabricating transition metal carbonitrides and provide a material platform for further study of the superconductivity of transition metal carbides.

Effect of heat input on ultrahard Fe-Cr-B-C-W-Mo-Nb hardfacing

Multicomponent alloys (Cr, Mo, W, Nb, C, B) nanostructured iron base with complex carboborides have been developed to provide great protection against abrasive wear to elements of agricultural and mining machines. These overlays are subject to severe material losses due to impact and abrasion of hard particles and therefore optimizing their wear resistance is critical when it comes to their lifespan, increasing it as a result. The objective of this work was to study the influence of heat input on the wear resistance through of the analysis of the solidification rate. In this sense, the increase of welding speed was produced a decrease of heat input and refined of microstructure. In order to explain these effects, an analysis was made of of the influence of welding speed on the geometry of the deposited metal, dilution with the base metal, microstructural evolution and hardness of iron-based nanostructured deposits with complex carbides. For this, four samples were welded with different speeds; these being 1, 2.5, 5 and 12 mm/s. A semi-automatic welding process was used with a 1.6 mm wire rope used to provide gas protection. The chemical composition was analyzed on a dilution free welded sample. For the each welded sample the dilution percentage was determined, the dimensional survey of the beads was carried out and the microstructure was characterized by X-ray diffraction and optical and scanning electron microscopy. In addition, Vickers microhardness tests were measured in the central area of the beads and the microhardness of phases were measured. The dilution of the deposited metals ranged from 17% to a maximum of 28%. A microstructure formed by a matrix with complex metal carbides and carboborides was observed. The hardness of the beads varied between 960 and 1350 HV2. The highest wear resistance was found in the sample with highest speed welding.

Nonhalogen Dry Etching of Metal Carbide TiAlC by Low-Pressure N2/H2 Plasma at Room Temperature.

Ternary metal carbide TiAlC has been proposed as a metal gate material in logic semiconductor devices. It is a hard-to-etch material due to the low volatility of the etch byproducts. Here, a simple, highly controllable, and dry etching method for TiAlC has been first presented using nonhalogen N2/H2 plasmas at low pressure (several Pa) and 20 °C. A capacitively coupled plasma etcher was used to generate N2/H2 plasmas containing active species, such as N, NH, and H to modify the metal carbide surface. The etch rate of TiAlC was obtained at 3 nm/min by using the N2/H2 plasma, whereas no etching occurred with pure N2 plasma or pure H2 plasma under the same conditions. The surface roughness of the TiAlC film etched by N2/H2 plasma was controlled at the atomic level. A smooth etched surface was achieved with a root-mean-square roughness of 0.40 nm, comparable to the initial roughness of 0.44 nm. The plasma properties of the N2/H2 plasmas were diagnosed by using a high-resolution optical emission spectrometer, detecting the NH molecular line at 336 nm. The etching behavior and plasma-surface reaction between N2/H2 plasma and TiAlC were investigated by using in situ spectroscopic ellipsometry, in situ attenuated total reflectance-Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy. The findings indicate that the N-H, C-N, and Ti(Al)-N bonds form on the TiAlC surface etched by the N2/H2 plasmas. The mechanism for etching of TiAlC involving transformation reactions between inorganic materials (metal carbides) and inorganic etchants (N2/H2 plasma) to form volatile organic compounds such as methylated, methyl-aminated, and aminated metals is proposed. Nonhalogen or nonorganic compound etchants were used during the etching process. The study provides useful insights into microfabrication for large-scale integrated circuits.

A Voltage Equalization Strategy for Series-Connected SiC MOSFET Applications

A novel clamped voltage equalization strategy is presented for series-connected Silicon Carbide (SiC) Metal–Oxide semiconductor Field-Effect transistors (MOSFETs) in this paper. Differences in device parameters and circuit asymmetry result in the uneven voltage distribution of series-connected SiC MOSFETs, which threatens the safe operation of the circuit. Dynamic voltage equalization is difficult to achieve due to the fast switching speed of SiC MOSFETs. This paper analyzes the switching characteristics and dynamic voltage equalization characteristics of SiC MOSFETs. Based on the analysis, an energy recovery strategy based on the clamping auxiliary circuit is proposed. A 2.8 kW (50 KHz) prototype is fabricated and tested to verify the strategy. Measurement results show that the maximum voltage stress is suppressed from 600 V to less than 320 V in the experimental condition.

Hydrogen Evolution Reactions of Hydrocarbons and Hydroborons Promoted by Superatomic Nbn- Clusters.

Hydrogen evolution reactions (HER) are crucial for producing renewable and ecological hydrogen energy. Here we report the finding that ethyl acetylene (C2H2), borane (B2H6), and benzene (C6H6) undergo drastic dehydrogenation reactions upon interaction with niobium cluster anions (Nbn-). This finding was enabled by our very sensitive and specialized mass spectrometer, which monitored the cluster ions and the resulting metal carbide and boride products in real time. Through mass spectrometry experiments and density functional theory computations, we delved into the varying reactivities of these common gas molecules with small Nbn- clusters and elucidated the underlying reaction mechanisms. These findings shed light on the HER mechanisms of hydrocarbon and hydroboron molecules on superatomic Nbn- clusters, furnishing valuable insights pertinent to the advancement of hydrogen energy resources.

Atomic Structures and Electronic Properties of Carbide Surfaces Unraveled by Scanning Tunneling Microscopy

AbstractCarbides, especially transition metal carbides (TMCs) and non‐metallic silicon carbides (SiCs), have registered wide applications in catalysis, superconductivity, semiconductor, and the like. Systematic studies have demonstrated the essential role of carbon in finetuning the atomic structures and electronic properties of carbides to improve their catalytic performance, superconducting transition temperature, and semiconductor bandgap. These advancements have positioned carbides as efficient substitutes for noble metals and crucial components in technological innovations. Scanning tunneling microscopy (STM) has emerged as a powerful technique in these studies, providing high‐resolution visualization and mapping of the surface geometric and electronic structures of these functionalized carbides. This review mainly focuses on the key aspects like the structures and properties of the aforementioned TMC and SiC surfaces unraveled by STM, aiming at understanding the fundamentals behind the state‐of‐the‐art technologies and advanced applications of the carbide‐involved functional systems. A very brief perspective on this topic is also provided at the end.

Wide-response-range and high-sensitivity piezoresistive sensors with triple periodic minimal surface (TPMS) structures for wearable human-computer interaction systems

High-performance pressure sensors are garnering interest in human-computer interaction technology, wearable devices, and bionic electronic skin development. However, highly sensitive sensors frequently have a limited response range. In this work, we developed composites with outstanding conductive network structures through the synergistic effect of transition metal carbides (MXene) and multi-walled carbon nanotubes (MWCNTs). Additionally, pressure sensors with various TPMS structures were prepared using innovative parametric design and Fused Deposition Molding (FDM) printing. Due to the stable synergistic conductive network and distinctive curved surface structure, the sensors exhibit exceptional sensing performance. This includes high sensitivity ranging from 4.67 MPa−1 to 7.03 MPa−1 (within the range of 0–0.1 MPa), a broad operating range (maximum 10 MPa), rapid response and recovery times (326 ms/193.4 ms), and long-term fatigue resistance (over 10,000 s cycles). By integrating mechanical properties, sensing properties, and finite element simulations, we analyzed the mechanism underlying the impact of various TPMS pore structures on the sensitivity and response range of the pressure sensor. In addition, the sensors were arrayed as 4 × 4 modules to successfully recognize a wide range of foot movements from different volunteers. These findings illuminate potential applications in human motion detection, healthcare rehabilitation, and artificial intelligence.

Selective reduction of CO2 to CO over alumina-supported catalysts of group 5 transition metal carbides

We show the applicability of a preparation method, previously reported for obtaining tailored bulk VCx catalysts, for alumina-supported G5TMCs. The characteristics of the G5TMCs/Al2O3 catalysts and their behaviour in the selective reduction of CO2 to CO through the RWGS reaction is reported. VCx/Al2O3 catalysts were active, stable and highly selective; meanwhile NbC/Al2O3 and TaC/Al2O3 were not active. VCx/Al2O3 catalysts exhibited selectivity to CO over 99.5 % at temperature above 773 K. The characteristics of alumina-supported vanadium carbide particles depended on the vanadium precursor and on the atmosphere used during the catalyst preparation. XPS characterization of VCx/Al2O3 catalysts revealed the presence of carbide species on surface before and after RWGS reaction. The catalytic behaviour of VCx/Al2O3 is analysed in the light of their characteristics and compared with bulk VCx counterparts. The most performant catalyst, VC(Pr)/Al2O3, was stable over 4 days at 723 K, with ∼100 % selectivity to CO and CO2 conversion of ∼11 %.

In Situ Observation of Microstructure and Precipitate Phase Transformation during the Solidification of Mg‐Containing GH3625 Alloy at Different Cooling Rates

In practical applications, intermetallic compounds like Laves phase and metal carbides adversely affect the performance of nickel‐based superalloys. Using a high‐temperature confocal laser scanning microscope, the solidification process of as‐cast GH3625 alloy containing Mg at different cooling rates (−20, −35, and −50 °C min−1) is studied. Fitting curves of the volume fraction of the solid phase with solidification temperature before and after Mg treatment are obtained. Trends of solid phase transformation rates with solidification temperature are determined. Differential scanning calorimetry is employed to analyze and statistically evaluate the melting temperature range and enthalpy of each phase during the melting process. Experimental results demonstrate that Mg treatment significantly accelerates the alloy solidification at the cooling rates of −20 and −35 °C min−1, while reducing the area of residual liquid phase at the same solidification temperature, disrupting the Laves/NbC eutectic relationship, and regularizing NbC morphology, transitioning its distribution from aggregation to dispersion. After Mg treatment, the precipitation of the Laves phase is significantly reduced. As a result, the influence mechanism of Mg treatment on the phase transformation and microstructure of GH3625 is clarified based on homogeneous nucleation theory.

2D MXene Biomaterials for Catalytic Medical Applications.

In recent years, two-dimensional transition metal carbides, nitrides, and carbonitrides, termed as MXenes, have been widely applied in energy storage, photocatalysis and biomedicine owing to their unique physicochemical properties of large specific surface area, high electrical conductivity, excellent optical performance, good stability, etc. Moreover, due to their strong light absorption capacity in the first and second near-infrared bio-window, and their ability of being simply functionalized with multiple organic/inorganic materials, MXene biomaterials have shown great potential in the field of catalytic therapy. This review will summarize the common catalytic mechanism of MXene biomaterials and their latest applications in catalytic medicine such as tumor therapy, antibacterial and anti-inflammatory, and present the current challenges and opportunities in clinical translation for future development to promote the advancement of MXene biomaterials in the field of catalytic medicine.

Enhanced removal of lead ions from wastewaters by electrochemical adsorption using nitrogen-doped Ti3C2Tx MXene

As a two-dimensional material containing transition metal carbides and nitrides, MXene is often used in capacitive deionization for its excellent hydrophilic and pseudocapacitive properties. Nitrogen doping is widely used to improve the adsorption properties of certain materials. However, the effect of nitrogen doping on the electrochemical adsorption properties of MXene remains unclear. In this work, nitrogen-doped Ti3C2Tx MXene was synthesized using a simple hydrothermal method to achieve highly selective and efficient removal of Pb(II) at a constant cell voltage. The concentration of Pb(II) decreased from 4.95 to 0.02 mg L−1 in a 100 mg L−1 NaCl supporting electrolyte after electrosorption. The removal efficiency of Pb(II) reached 99.5%, whereas it was only 15.2% for Na+. The introduction of nitrogen functional groups increased the electrical conductivity and layer spacing of MXene, thereby improving the pseudocapacitive adsorption performance in the presence of Pb(II). The complexation function of the Ti-OH group on nitrogen-doped Ti3C2Tx surface increased and contributed to the selective adsorption of Pb(II). The removal efficiency of Pb(II) increased with increasing solution pH and cell voltage, reaching the maximum value at pH 5.0 and 1.5 V, respectively. The effect of supporting electrolyte type on the removal of Pb(II) was negligible. In addition, the removal efficiency for mixed heavy metal ion solutions, including Cu(II), Ni(II), and Pb(II), exceeded 79.0%. It exhibited the highest removal efficiency for Pb(II) at 97.9%. After five cycles of electrochemical adsorption–desorption, the nitrogen-doped Ti3C2Tx maintained a stable Pb(II) removal efficiency of 97.0%. This work provides a promising material for the electrochemical removal of low-concentration heavy metal ions from wastewaters.

Enhancing Conductivity in Silicon Heterojunction Solar Cells with Silver Nanowire-Assisted Ti3C2Tx MXene Electrodes for Cost-Effective and Scalable Photovoltaics.

Silicon heterojunction (SHJ) solar cells have set world-record efficiencies among single-junction silicon solar cells, accelerating their commercial deployment. Despite these clear efficiency advantages, the high costs associated with low-temperature silver pastes (LTSP) for metallization have driven the search for more economical alternatives in mass production. 2D transition metal carbides (MXenes) have attracted significant attention due to their tunable optoelectronic properties and metal-like conductivity, the highest among all solution-processed 2D materials. MXenes have emerged as a cost-effective alternative for rear-side electrodes in SHJ solar cells. However, the use of MXene electrodes has so far been limited to lab-scale SHJ solar cells. The efficiency of these devices has been constrained by a fill factor (FF) of under 73%, primarily due to suboptimal charge transport at the contact layer/MXene interface. Herein, a silver nanowire (AgNW)-assisted Ti3C2Tx MXene electrode contact is introduced and explores the potential of this hybrid electrode in industry-scale solar cells. By incorporating this hybrid electrode into SHJ solar cells, 9.0 cm2 cells are achieved with an efficiency of 24.04% (FF of 81.64%) and 252 cm2 cells with an efficiency of 22.17% (FFof 76.86%), among the top-performing SHJ devices with non-metallic electrodes to date. Additionally, the stability and cost-effectiveness of these solar cells are discussed.

Catalyst breakthroughs in methane dry reforming: Employing machine learning for future advancements

Rising levels of atmospheric carbon dioxide (CO2) and methane (CH4) have sparked the interest of researchers in resolving this issue. Various technologies have been utilized such as dry reformation of methane (DRM), that turns these greenhouse gases (GHGs) into syngas. Numerous studies have been done in recent years to produce efficient and competitive catalysts for DRM. However, a “state of the art” review is still required due to a lack of literature on improvements and scalability of robust catalytic systems. This study aims to evaluate recent advancements in catalyst formulations, their activities, stability, and selectivity. We have discussed a variety of materials, including Metal-Organic Frameworks (MOF), a type of two-dimensional transition metal carbides and nitrides (MXene), reducible and irreducible metal oxides, transition metal oxides, zeolites, carbon, and biochar-based catalysts, which are responsible for improving the effectiveness of the DRM process. Furthermore, machine learning (ML) approaches are highlighted for their potential in catalyst design and optimization, providing increased accuracy and efficiency. This review highlights major enhancements to the DRM method, which result in higher hydrogen yield and catalyst stability. Novel catalysts have been created to tackle crucial problems including coking and sintering, which are necessary to progress commercialization. To ensure successful commercial application, future research should concentrate on finding catalysts with excellent features that are also economically viable. This study provides a significant resource for future catalyst development and promotes greater cooperation between academic and commercial communities.

Comparative study of hydrogen storage on nickel and palladium decorated metal carbide nanotubes: A DFT approach

Comparative study of hydrogen storage on nickel and palladium decorated metal carbide nanotubes: A DFT approach

Rare-Earth (R) In-Plane Ordering in Novel (Mo, R, Nb)4AlC3 Quinary o-MAX Nanolaminates and their 2D Derivatives.

Nanolamellar transition metal carbides are gaining increasing attentions because of the promising application in energy storage of their 2D derivatives. There are in-plane and out-of-plane atomic ordered occupations, which is thought to only be formed in separated systems due to totally different origins and crystallographic structure. In present work, starting from (Mo, Nb)4AlC3 o-MAX phase where out-of-plane ordered occupation is experimentally and theoretically proved for Mo/Nb atoms, rare-earth elements (R = Y, Gd-Tm, Lu) are introduced, and the novel Mo3.33- xR0.67NbxAlC3 (x = 1, 1.25, 1.5, 1.75, 2, 2.25, and 2.5) super-ordered (s-) MAX phase is synthesized, where R is ordered at the outer layer in the strict stoichiometry meanwhile Mo/Nb maintains the out-of-plane ordered occupation. By R introduction, s-MAX is easier to be delaminated to obtain the s-MXene with the topochemical ordered vacancies, leading into the enhanced supercapacitance of 114.9 F g-1 in Mo1.33Nb2C3 s-MXene compared with 95.1 F g-1 in Mo2Nb2C3 o-MXene. By Pt anchoring, very low overpotential of 22mV at a current density of 10mA cm-2 is achieved for HER applications. This study demonstrates a novel variety of s-MAX phase and seeks to inspire further exploration of the ordered MAX and MXene families.