Search Results (31)

The photocatalytic performance of heterojunctions is often restricted by inferior contact interface and low charge transfer efficiency. In this work, Ti₃C₂O MXene was crafted with AgI/MoS₂ to produce a Z-scheme heterojunction (AgI/MoS₂/Ti₃C₂O). Interfacial electric fields and chemical bonds were proven to exist in the heterojunction. The interfacial electric fields supplied a powerful driving force, and the interfacial Ti-O-Mo bonds served as an atomic-level channel for synergistically expediting the vectorial transfer of photogenerated carriers. As a result, AgI/MoS₂/Ti₃C₂O exhibited significantly improved photocatalytic activity, demonstrating a high H₂O₂ production rate of 700 μmol·g⁻¹·h⁻¹ and a rapid degradation of organic pollutants. Full article

Polyimide (PI), owing to its high heat resistance and low density, is often employed as a substitute for metallic materials in high-temperature environments, such as aircraft engines, bearings, and gears. However, the relatively high friction coefficient of pure PI limits its application under harsh conditions. Therefore, this study synthesized a composite lubricant with binary fillers to improve this performance. This study employed the hydrothermal method to synthesize MoS₂/MXene composite lubricating fillers and systematically investigated the high-temperature tribological properties of PI composites reinforced with these fillers. The results demonstrated that the optimal PI composite containing 5% MoS₂/MXene exhibited a 14 °C increase in initial decomposition temperature compared to pure PI. Additionally, its thermal conductivity was enhanced by 36%, while the hardness (0.398 GPa) and elastic modulus (6.294 GPa) were elevated by 12.4% and 18.6%, respectively, relative to the pure PI. In terms of tribological behavior, all composite formulations displayed typical temperature-dependent friction characteristics. It is worth noting that MXene’s high hardness and thermal conductivity inhibited the occurrence of abrasive wear. At the same time, the substrate was strengthened, and thermal resistance was enhanced, thereby delaying the plastic deformation of the material at high temperatures. Full article

MXenes have emerged as promising candidates for energy storage and catalyst design. Through detailed density functional theory (DFT) calculations, we designed a series of new 2D composite MXene-based nanomaterials by covering excellent TM₃N₂ MXenes (TM = Nb, Ta, Mo, and W) with graphene or buckled silicene. Our findings demonstrate that this coating can lead to high catalytic activity for hydrogen evolution reactions (HER) in these composite MXene-based systems, with silicene exhibiting superior performance compared to graphene. The relevant carbon and silicon atoms in the coated materials serve as active sites for HER due to complex electron transfer processes. Additionally, doping N or P atoms into graphene/silicene, which have similar atomic radii, but larger electronegativity than C/Si atoms, can further enhance the HER activity of adjacent carbon or silicon atoms, thus endowing the composite systems with higher HER catalytic performance. Coupled with their high stability and metallic conductivity, all these composite systems show great potential as electrocatalysts for HER. These remarkable findings offer new strategies and valuable insights for designing non-precious and highly efficient MXene-based HER electrocatalysts. Full article

Previous studies have demonstrated that underwater low-temperature plasma is effective for synthesizing nanomaterials by generating plasma discharges between metal electrodes submerged in water. This study extends this approach to the one-step synthesis of MXenes containing titanium, molybdenum, and titanium–molybdenum composites through pulsed discharges in carbon tetrachloride, an oxygen-free, non-flammable solvent characterized by a high boiling point and low permittivity. By employing titanium and molybdenum electrodes in various configurations, three MXene samples were synthesized: Ti₂CT_X, Mo₂CT_X, and Mo₂TiC₂T_X. Characterization techniques, including UV-Vis spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, confirmed the successful synthesis of high-purity MXenes with distinct structural and optical properties. Notably, the bandgap values of the synthesized MXenes were determined as 1.71 eV for Ti₂CT_X, 1.42 eV for Mo₂TiC₂T_X, and 1.07 eV for Mo₂CT_X. The photocatalytic performance of the synthesized MXenes was evaluated, showing a removal efficiency of 65% to 98% for dye mixtures, with methylene blue showing the highest degradation rate. This plasma-assisted method offers a scalable, precursor-free route for the synthesis of MXenes with potential applications in energy storage, environmental remediation, and optoelectronics due to their tunable bandgaps and high catalytic activity. Full article

We investigate the structural, electronic, optical, and thermoelectric properties of three compositions of Mo₂C-MXenes (Mo₂CF₂, Mo₂C(OH)₂, and Mo₂CO₂) from monolayer to multilayer by first principles calculation within Density Functional Theory (DFT) and Boltzmann transport theory. Firstly, the atomic structures of Mo₂C-MXenes are optimized, and their respective structures are created with comparative research. Secondly, their electronic band structures and optical properties are studied in detail. The estimation of the bandgap energy of Mo₂C-MXenes with its functionalization reveal that most Mo₂CF₂ and Mo₂C(OH)₂ layers are semiconductors, while Mo₂CO₂ behaves as a metal. The electrical and optical properties can be altered by controlling the on-surface functional groups and the number of layers. Computation of the thermoelectric (TE) properties of Mo₂C-MXenes reveals that, upon heating to 600 K, Mo₂CF₂ and Mo₂C(OH)₂ exhibit a high Seebeck coefficient and a relatively high electrical conductivity. The Seebeck coefficient reaches ~400 µV K⁻¹ at room temperature for all layers of Mo₂CF₂ MXenes. Our results prove that Mo₂CF₂ is considered a promising material for thermoelectric devices, while Mo₂CO₂ does not possess better thermoelectric performance. Mo₂C-MXenes from monolayer to multilayer have outstanding properties, such as flexible bandgap energy and high thermal stability, making them promising candidates for many applications, including energy storage and electrode applications. Full article

We report a computational study of the bending deformation of two-dimensional nanoribbons by classical molecular dynamics methods. Two-dimensional double transition metal carbides, together with monometallic ones, belong to the family of novel nanomaterials, so-called MXenes. Recently, it was reported that within molecular dynamics simulations, Ti₄C₃ MXene nanoribbons demonstrated higher resistance to bending deformation than thinner Ti₂C MXene and other two-dimensional materials, such as graphene and molybdenum disulfide. Here, we apply a similar method to that used in a previous study to investigate the behavior of Mo₂Ti₂C₃ nanoribbon under bending deformation, in comparison to the Ti₄C₃ sample that has a similar structure. Our calculations show that Mo₂Ti₂C₃ is characterized by higher bending rigidity at $D_{{\mathrm{Ti}}_2{\mathrm{Mo}}_2{\mathrm{C}}_3}\approx 92.15$ eV than monometallic Ti₄C₃ nanoribbon at $D_{{\mathrm{Ti}}_4{\mathrm{C}}_3}\approx 72.01$ eV, which has a similar thickness. Moreover, approximately the same magnitude of critical central deflection of the nanoribbon before fracture was observed for both Mo₂Ti₂C₃ and Ti₄C₃ samples, $w_c\approx 1.7$ nm, while Mo₂Ti₂C₃ MXene is characterized by almost two times higher critical value of related external force. Full article

A new two-dimensional (2D) non-MXene transition metal carbide, Mo₃C₂, was found using the USPEX code. Comprehensive first-principles calculations show that the Mo₃C₂ monolayer exhibits thermal, dynamic, and mechanical stability, which can ensure excellent durability in practical applications. The optimized structures of Li_x@(3×3)-Mo₃C₂ (x = 1–36) and Na_x@(3×3)-Mo₃C₂ (x = 1–32) were identified as prospective anode materials. The metallic Mo₃C₂ sheet exhibits low diffusion barriers of 0.190 eV for Li and 0.118 eV for Na and low average open circuit voltages of 0.31–0.55 V for Li and 0.18–0.48 V for Na. When adsorbing two layers of adatoms, the theoretical energy capacities are 344 and 306 mA h g⁻¹ for Li and Na, respectively, which are comparable to that of commercial graphite. Moreover, the Mo₃C₂ substrate can maintain structural integrity during the lithiation or sodiation process at high temperature. Considering these features, our proposed Mo₃C₂ slab is a potential candidate as an anode material for future Li- and Na-ion batteries. Full article

Antibiotic abuse, particularly the excessive use of tetracycline (TC), a drug with significant environmental risk, has gravely harmed natural water bodies and even posed danger to human health. In this study, a three-dimensional self-supported MoS₂/MXene nanohybrid with an expanded layer spacing was synthesized via a facile one-step hydrothermal method and used to activate peroxydisulfate (PDS) for the complete degradation of TC. The results showed that a stronger •OH signal was detected in the aqueous solution containing MoS₂/MXene, demonstrating a superior PDS activation effect compared to MoS₂ or Ti₃C₂T_X MXene alone. Under the conditions of a catalyst dosage of 0.4 g/L, a PDS concentration of 0.4 mM, and pH = 5.0, the MoS₂/MXene/PDS system was able to fully eliminate TC within one hour, which was probably due to the presence of several reactive oxygen species (ROS) (•OH, SO₄^•−, and O₂^•−) in the system. The high TC degradation efficiency could be maintained under the influence of various interfering ions and after five cycles, indicating that MoS₂/MXene has good anti-interference and reusability performance. Furthermore, the possible degradation pathways were proposed by combining liquid chromatography–mass spectrometry (LC-MS) data and other findings, and the mechanism of the MoS₂/MXene/PDS system on the degradation process of TC was elucidated by deducing the possible mechanism of ROS generation in the reaction process. All of these findings suggest that the MoS₂/MXene composite catalyst has strong antibiotic removal capabilities with a wide range of application prospects. Full article

Precious metals exhibit promising potential for the hydrogen evolution reaction (HER), but their limited abundance restricts widespread utilization. Loading precious metal nanoparticles (NPs) on 2D/2D heterojunctions has garnered considerable interest since it saves precious metal consumption and facilitates unidirectional electron transmission from semiconductors to active sites. In this study, Ru NPs loaded on MXenes Mo₂C by an in-site simple strategy and then formed 2D/2D heterojunctions with 2D g-C₃N₄ (CN) via electrostatic self-assembly were used to enhance photocatalytic H₂ evolution. Evident from energy band structure analyses such as UV-vis and TRPL, trace amounts of Ru NPs as active sites significantly improve the efficiency of the hydrogen evolution reaction. More interestingly, MXene Mo₂C, as substrates for supporting Ru NPs, enriches photoexcited electrons from CN, thereby enhancing the unidirectional electron transmission. As a result, the combination of Ru-Mo₂C and CN constructs a composite heterojunction (Ru-Mo₂C@CN) that shows an improved H₂ production rate at 1776.4 μmol∙g⁻¹∙h⁻¹ (AQE 3.58% at 400 nm), which is facilitated by the unidirectional photogenerated electron transmission from the valence band on CN to the active sites on Ru (CN→Mo₂C→Ru). The study offers fresh perspectives on accelerated unidirectional photogenerated electron transmission and saved precious metal usage in photocatalytic systems. Full article

The combination of two-dimensional material MXene and one-dimensional metal oxide semiconductor can improve the carrier transmission rate, which can effectively improve sensing performance. We prepared a trimethylamine gas sensor based on MoO₃ nanofibers and layered Ti₃C₂T_x MXene. Using electrospinning and chemical etching methods, one-dimensional MoO₃ nanofibers and two-dimensional Ti₃C₂T_x MXene nanosheets were prepared, respectively, and the composites were characterized via XPS, SEM, and TEM. The Ti₃C₂T_x MXene–MoO₃ composite material exhibits excellent room-temperature response characteristics to trimethylamine gas, showing high response (up to four for 2 ppm trimethylamine gas) and rapid response–recovery time (10 s/7 s). Further, we have studied the possible sensitivity mechanism of the sensor. The Ti₃C₂T_x MXene–MoO₃ composite material has a larger specific surface area and more abundant active sites, combined with p–n heterojunction, which effectively improves the sensitivity of the sensor. Because of its low detection limit and high stability, it has the potential to be applied in the detection system of trimethylamine as a biomarker in exhaled air. Full article

MXene has emerged as a highly promising two-dimensional (2D) layered material with inherent advantages as an electrode material, such as a high electrical conductivity and spacious layer distances conducive to efficient ion transport. Despite these merits, the practical implementation faces challenges due to MXene’s low theoretical capacitance and issues related to restacking. In order to overcome these limitations, we undertook a strategic approach by integrating Ti₃C₂T_x MXene with cobalt molybdate (CoMoO₄) nanoparticles. The CoMoO₄ nanoparticles bring to the table rich redox activity, high theoretical capacitance, and exceptional catalytic properties. Employing a facile hydrothermal method, we synthesized CoMoO₄/Ti₃C₂T_x heterostructures, leveraging urea as a size-controlling agent for the CoMoO₄ precursors. This innovative heterostructure design utilizes Ti₃C₂T_x MXene as a spacer, effectively mitigating excessive agglomeration, while CoMoO₄ contributes its enhanced redox reaction capabilities. The resulting CoMoO₄/T_i3C₂T_x MXene hybrid material exhibited 698 F g⁻¹ at a scan rate of 5 mV s⁻¹, surpassing that of the individual pristine Ti₃C₂T_x MXene (1.7 F g⁻¹) and CoMoO₄ materials (501 F g⁻¹). This integration presents a promising avenue for optimizing MXene-based electrode materials, addressing challenges and unlocking their full potential in various applications. Full article

Real-time sensing of hydrogen sulfide (H₂S) at room temperature is important to ensure the safety of humans and the environment. Four kinds of different nanocomposites, such as MXene Ti₃C₂T_x, Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄, were synthesized using the hydrothermal method in this paper. Initially, the intrinsic properties of the synthesized nanocomposites were studied using different techniques. P-type butane and H₂S-sensing behaviors of nanocomposites were performed and analyzed deeply. Four sensor sheets were fabricated using a spin-coating method. The gas sensor was distinctly part of the chemiresistor class. The MXene Ti₃C₂T_x/NiCo₂O₄-based gas sensor detected the highest response (16) toward 10 ppm H₂S at room temperature. In comparison, the sensor detected the highest response (9.8) toward 4000 ppm butane at 90 °C compared with the other three fabricated sensors (Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄). The MXene Ti₃C₂T_x/NiCo₂O₄ sensor showed excellent responses, minimum limits of detection (0.1 ppm H₂S and 5 ppm butane), long-term stability, and good reproducibility compared with the other fabricated sensors. The highest sensing properties toward H₂S and butane were accredited to p–p heterojunctions, higher BET surface areas, increased oxygen species, etc. These simply synthesized nanocomposites and fabricated sensors present a novel method for tracing H₂S and butane at the lowest concentration to prevent different gas-exposure-related diseases. Full article

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 Ti₃C₂T_x to improve the conductivity of a MoSe_2-based electrocatalyst. Finally, MoSe₂@Ti₃C₂T_x was successfully synthesized, according to the control of the additional amount of Ti₃C₂T_x, to form a proper MoSe₂/ Ti₃C₂T_x heterostructure with a better electrochemical HER performance. As obtained MoSe₂@4 mg-Ti₃C₂T_x achieved a low overpotential, a small Tafel slope and this work offers additional insight into broadened MoSe₂ and MXenes-based catalyst’s electrochemical application. Full article

Utilizing interface engineering to construct abundant heterogeneous interfaces is an important means to improve the absorbing performance of microwave absorbers. Here, we have prepared the MXene/MoS₂-ReS₂ (MMR) composite with rich heterogeneous interfaces composed of two-dimensional Ti₃C₂Tx MXene and two-dimensional transition metal disulfides through a facile hydrothermal process. The surface of MXene is completely covered by nanosheets of MoS₂ and ReS₂, forming a hybrid structure. MRR exhibits excellent absorption performance, with its strongest reflection loss reaching −51.15 dB at 2.0 mm when the filling ratio is only 10 wt%. Meanwhile, the effective absorption bandwidth covers the range of 5.5–18 GHz. Compared to MXene/MoS₂ composites, MRR with a MoS₂-ReS₂ heterogeneous interface exhibits stronger polarization loss ability and superior absorption efficiency at the same thickness. This study provides a reference for the design of transition metal disulfides-based absorbing materials. Full article

The chemoresistive properties of multilayer titanium-containing Ti₂CT_x and Ti₃C₂T_x MXenes, synthesized by etching the corresponding MAX phases with NaF solution in hydrochloric acid, and the composites based on them, obtained by partial oxidation directly in a sensor cell in an air flow at 150 °C, were studied. Significant differences were observed for the initial MXenes, both in microstructure and in the composition of surface functional groups, as well as in gas sensitivity. For single Ti₂CT_x and Ti₃C₂T_x MXenes, significant responses to oxygen and ammonia were observed. For their partial oxidation at a moderate temperature of 150 °C, a high humidity sensitivity (T, RH = 55%) is observed for Ti₂CT_x and a high and selective response to oxygen for Ti₃C₂T_x at 125 °C (RH = 0%). Overall, these titanium-containing MXenes and composites based on them are considered promising as receptor materials for low temperature oxygen sensors. Full article