Pristine MXene Research Articles

Fast fabrication of freestanding MXene-ZIF-8 dual-layered membranes for H2/CO2 separation

As one of the green, renewable, and clean energy resources, hydrogen is widely developed and utilized throughout the world. Highly efficient membrane separation for hydrogen production is required to give promising gas permeance with enough H2 selectivity. The membranes are desired to be produced in large-scale, fast and facile methods. Here we report for the first time a kind of freestanding MXene-ZIF-8 dual-layered membrane for hydrogen separation. Fast synthesis of such membranes is realized by combining electrophoretic deposition (EPD) and fast current-driven synthesis (FCDS), achieving the assemble of MXene layer and growth of ZIF-8 layer, respectively, overcoming the traditional time-consuming vacuum filtration methods and solvothermal synthesis. The MXene-ZIF-8 dual-layered membrane prepared within 20 min exhibits significantly improved gas separation performance, whose H2/CO2 selectivity increases from 44 for the pristine MXene membrane to 77 with H2 permeance of 5.97 × 10−8 mol m−2 s−1 Pa−1. This concept of structure design of membrane can also be extended to other dual-layered membranes, including various 2D nanosheet layers combined with different MOF layers.

Mo1.33CTz–Ti3C2Tz mixed MXene freestanding films for zinc-ion hybrid supercapacitors

The high demand on fast rechargeable batteries and supercapacitors combined with the limited resources of their active materials (e.g. Li and Co) motivate the exploration of sustainable energy storage systems such as Zn-ion hybrid supercapacitors. MXenes are two-dimensional materials with outstanding properties such as high conductivity and capacitance which enhance their performance in energy storage devices. Herein, we report on the use of freestanding Mo1.33CTz–Ti3C2Tz mixed MXene films in Zn-ion hybrid supercapacitors. The mixed MXene films are prepared from pristine MXene suspensions using a one-step vacuum filtration approach. The mixed MXene delivers capacities of about 159 and 59 mAh/g at scan rates of 0.5 and 100 mV/s, respectively. These capacity values are higher than the pristine MXene films and previously reported values for MXene electrodes in Zn-ion supercapacitors. Furthermore, the electrodes offer a promising capacity retention of about 90% after 8,000 cycles. In addition, the mixed MXene features energy densities of about 103 and 38 Wh/kg at power densities of 0.143 and 10.6 kW/kg, respectively. Insights into the effect of electrode thickness on rate performance and the mechanism of charge storage are also discussed. This study opens a venue for the use of Mo1.33CTz–Ti3C2Tz mixed MXene electrodes in sustainable energy storage systems with high energy density and power density.

In situ polymerized polyaniline/MXene (V2C) as building blocks of supercapacitor and ammonia sensor self-powered by electromagnetic-triboelectric hybrid generator

This paper reports in situ polymerization of polyaniline (PANI)/MXene (V 2 C) composites as building blocks of supercapacitor and ammonia sensor self-powered by electromagnetic-triboelectric hybrid generator. The high accessible surface of MXene produced abundant high reactivity and electronegativity sites, which could promote or induce the polymerization of aniline on its surface and the polymerization of aniline on its surface could prevent its re-stacking and enhance its electrochemical activity, which could significantly improve the performance of ammonia sensor and supercapacitor. The working principle of the integrated self-power system is to use the hybrid nanogenerator of triboelectric nanogenerators (TENGs) and electromagnetic generator (EMGs) to charge the supercapacitor for driving the ammonia sensor. The supercapacitor utilized PANI/MXene as anode and active carbon as cathode, which displays a capacitance of 337.5 F/g at the current density of 1 A/g, a considerable energy density of 11.25 Wh/kg and a power density of 415.38 W/kg. The sensing material of PANI/MXene nanosheets have an eye catching response value ((R g -R a )/R a = 14.9% @ 1 ppm NH 3 ), good stability (more than 60 days) and fast response/recovery time (9 s/9 s @ 1 ppm NH 3 ), which is much better than the pristine PANI and MXene nanosheets. This work provided a candidate of PANI/MXene for constructing supercapacitor and sensing elements, which opened up an avenue for the integration of self-power gas sensing for industrial and agricultural pollution. • In situ polymerization of PANI/MXene composites as building blocks of supercapacitor and ammonia sensor. • The PANI/MXene composite film-based NH 3 sensor was self-powered by a hybrid power generation system. • The hybrid power generation system is constructed by triboelectric nanogenerators and electromagnetic generator. • A series of detection and alarm systems are designed to realize the real-time transmission and sharing of data.

Preparation of functionalized MXene-stitched-graphene oxide/poly (ethylene-co-acrylic acid) nanocomposite with enhanced hydrogen gas barrier properties

The storage of H2 is one of the critical issues to be resolved to expand H2-based energy. Herein, MXene was employed in combination with GO for the first time for H2 gas barrier coating on nylon 6 substrate (commonly used in storage tanks). A facile two-step method was acquired to covalently bond MXene and GO through 3-aminopropyl triethoxysilane (APTES) by employing carbodiimide reaction. The MXene-GO hybrid nanofiller (f-MXene-GO) exhibited a higher gallery gap between the nanosheets than that of the pristine MXene and GO. Besides, GO was also partially reduced by the amine functional groups of APTES. To the best of our knowledge, the stitching of MXene and GO using APTES has not yet been discussed in the literature. When f-MXene-GO was dispersed in poly (ethylene-co-acrylic acid) (EAA), a significant improvement in the mechanical properties was observed. An increase in the gallery gap between the MXene layers in f-MXene-GO/EAA nanocomposite as compared to MXene/EAA suggested the effectiveness of APTES grafting to enhance the interaction with EAA. MXene/EAA exhibited a higher H2 gas barrier and mechanical properties than GO/EAA, whereas the adhesion of MXene/EAA to the nylon 6 substrate was weak. f-MXene-GO/EAA exhibited a judicious combination of both barrier and adhesion properties. The 10 wt% f-MXene-GO/EAA coated layer showed a very low H2 permeability coefficient (0.03 cc.mm.m−2.d−1.atm−1) and a significant 89% reduction in the H2 gas transmission rate with respect to nylon 6.

Removal of heavy metal cations and co-existing anions in simulated wastewater by two separated hydroxylated MXene membranes under an external voltage

The removal of heavy metal cations and co-existing anions represents one of the promising pathways to produce purified water for industry. Laminar MXene membrane has attracted tremendous research interest in the separation field in the past decade. The thermal self cross-linking MXene membrane has been proven to exhibit good anti-swelling performance. However, the decrease of negative charge during self-crosslinking leads to decreasing ion separation performance due to fading adsorption and/or weakened surface-charged controlling effect. To regenerate the surface charge, the hydroxylation of MXene membrane is adopted by substituting –F with –OH using the alkali of KOH. The resultant hydroxylated MXene membrane demonstrates overall better performance than the pristine MXene membrane in wettability and Zeta potential, promoting the rejection and separation of ions. When two selective membranes are applied to remove the heavy metal cations (Pb2+, Cu2+, and Cd2+) and co-existing anions (Cl− and/or NO3−) under the electronic field with appropriate voltage, the rejection of 99.5% can be obtained at 12 V for a 383 nm-thick hydroxylated MXene membrane, higher than that of pristine MXene membrane. As a result, the co-existing anions were also excluded at ~97% via increasing surface-charged controlling effect. Moreover, the hydroxylated MXene membrane also shows selective separation permeance on Na+/Pb2+, Na+/Cu2+, and Na+/Cd2+ pairs. By controlling the interlayer spacing through thermal self-linking route, good operational durability and reproducibility are also achieved for the hydroxylated MXene membrane during the 70-min test. These highlight the potential of developing and applying 2D laminar membrane for separation and treatment of wastewater.

Enhanced NO2 gas-sensing performance of 2D Ti3C2/TiO2 nanocomposites by in-situ formation of Schottky barrier

Two-dimensional (2D) Ti3C2 MXene, derived from the Ti3AlC2 MAX phase, is a potential candidate for gas sensing materials due to its high conductivity, but it has a shortcoming of weak sensitivity towards gases. Here, we firstly synthesized Ti3C2/TiO2 nanocomposites by in-situ growth of TiO2 on the surface of multilayer Ti3C2 MXene via a hydrothermal oxidation process, and investigated the gas-sensing performances (involving response, operation temperature and selectivity) of Ti3C2/TiO2 composites by combining experiments and first-principles calculations. The experimental results show that the hydrothermal oxidation temperature plays a key role in the morphology evolution and gas-sensing performance of Ti3C2/TiO2 composites. Compared to the pristine Ti3C2, the Ti3C2/TiO2 composites display outstanding response to NO2 gas due to the formation of a Schottky barrier at the Ti3C2/TiO2 interface, as a result of that the excellent response of ~ 1.13 to 5 ppm NO2 is achieved at room temperature. In particular, the optimal Ti3C2/TiO2 composite presents higher response value (86 times) and faster response and recovery time (2 and 3.8 times) to 100 ppm NO2 than pristine Ti3C2 at optimum temperatures, and shows good selectivity and linear response to NO2 gas. This work provides a simple process to in-situ form the Schottky barrier for improving the gas-sensing performance of pristine MXene in practical applications.

Oxidized-co-crumpled multiscale porous architectures of MXene for high performance supercapacitors

MXene, an example of two-dimensional (2D) transition metal carbides, is a promising electrode material for batteries and supercapacitors because of its excellent electrochemical properties derived from transition metal carbide/nitride constituents and its high electrical conductivity. However, similar to other 2D nanomaterials, MXene-based electrodes have a notable shortcoming of reduced specific surface area and reduced ion diffusion due to the self-restacking of MXene nanosheets. Here, to overcome these limitations, we present a novel method to create oxidized-co-crumpled multiscale porous architectures of MXene by a sequential process consisting of partial oxidation by hydrogen peroxide and then flocculation in acid. These treatments result in simultaneous generation of mesopores by oxidation and macropores caused by structural crumpling. This oxidized-co-crumpled MXene has a five times larger specific surface area (72 m2/g) than pristine MXene. In addition, the capacitance performance (307 F/g at 20 mV/s under 1 M H2SO4) and the capacitance at a higher scan rate (225 F/g at 100 mV/s) are improved. Additionally, after 6000 cycles, 87.6% of the capacitance is retained. Such an improvement in the properties is attributed to the structural advantages of the multiscale porous oxidized-co-crumpled MXene, wherein ion diffusion through mesopores is facilitated, while the crumpled macropores prevent re-stacking. Overall, this study demonstrates a promising strategy to create MXene-based high performance electrode materials for a variety of electrochemical applications.

Experimental and Computational Analysis of MnO2@V2C-MXene for Enhanced Energy Storage.

Herein, we studied the novel and emerging group of 2D materials namely MXene along with its nanocomposites. This work entails detailed experimental as well as computational study of the electrochemical behavior of vanadium carbide (V2CTx) MXene and MnO2-V2C nanocomposite with varying percentages of MnO2. A specific capacitance of 551.8 F/g was achieved for MnO2-V2C nanocomposite in 1 M KOH electrolyte solution, which is more than two times higher than the gravimetric capacitance of 196.5 F/g obtained for V2C. The cyclic stability achieved for the MnO2-V2C nanocomposite resulted in a retentivity of 96.5% until 5000 cycles. The c-lattice parameter achieved for MXene is 22.6 Å, which was 13.01 Å for MAX phase. The nanocomposite resulted in a c-lattice parameter of 27.2 Å, which showed that the spatial distance between the MXene layers was efficiently obtained. The method of wet etching was used for the preparation of pristine MXene and the liquid phase precipitation method was opted for the synthesis of the MnO2-V2C nanocomposite. Density functional theory calculation was exercised so as to complement the experimental results and to understand the microscopic details, such as structure stability and electronic structure. The current report presents a comprehensive experimental and computational study on 2D MXenes for future energy storage applications.

Industry‐Scale and Environmentally Stable Ti3C2Tx MXene Based Film for Flexible Energy Storage Devices

AbstractMXenes, 2D transition metal carbides, and nitrides have attracted tremendous interest because of their metallic conductivity, solution processability, and excellent merits in energy storage and other applications. However, the pristine MXene films often suffer from poor ambient stability and mechanical properties that stem from their polar terminal groups and weak interlayer interactions. Here, a heteroatom doping strategy is developed to tailor the surface functionalities of MXene, followed by the addition of large‐sized reduced graphene oxide (rGO) as conductive additives to achieve a scalable production of S, N‐MXene/rGO (SNMG‐40) hybrid film with high mechanical strength (≈45 MPa) and energy storage properties (698.5 F cm−3). Notably, the SNMG‐40 film also demonstrates long‐term cycling stability (≈98% capacitance retention after 30 000 cycles), which can be maintained under ambient condition or immersed in H2SO4 electrolyte for more than 100 days. The asymmetric supercapacitor (aMGSC) based on SNMG‐40 film shows an ultrahigh energy density of 22.3 Wh kg−1, which is much higher than those previously reported MXene‐based materials. Moreover, the aMGSC also provides excellent mechanical durability under different deformation conditions. Thus, this strategy makes MXene materials more competitive for real‐world applications such as flexible electronics and electromagnetic interference shielding.

First-principle study of electronic properties and quantum capacitance of lithium adsorption on pristine and vacancy-defected O-functionalized Ti2C MXene

The electronic structure, surface charge storage and quantum capacitance of lithium adsorption on pristine and vacancy-defected Ti2CO2 MXene are theoretically investigated by density functional theory. Negative adsorption energies (Eads) of pristine Ti2CO2 (PT) and C-vacancy Ti2CO2 (VT) monolayers adsorbed by Li atom indicate that the adsorption processes of Li atom on systems are exothermic and favorable to adsorption. The most stable configurations are confirmed for the Li-adsorbed PT and VT monolayers. Pristine Ti2CO2 (PT) monolayer is a semiconductor with the bandgap of 0.2035 eV, while C-vacancy Ti2CO2 (VT) monolayer has the metallic nature. The adsorption of Li atom on PT monolayer makes the system undergo the semiconductor-metal transition, while the adsorption of Li atom on VT monolayer doesn’t change the metal nature. The magnetism is observed for the system with Li atom directly adsorbed on top of hollow site (VT-LH), and the total magnetic moments is 0.18 μB. Charge density differences of the adsorption of Li atom on PT and VT monolayers are further explored. The introduction of C-vacancy improves the quantum capacitances of the Li-adsorbed systems at 0 V, and Li-adsorbed PT and VT monolayers have high quantum capacitance because of the large density of states near Fermi level, and are suitable for cathode material.

Density functional theory studies of transition metal doped Ti3N2 MXene monolayer

Spin-polarized density functional theory calculations with van der Waals correction were applied to investigate the presence of transition metal dopant atoms (Fe, Co, Ni, Pd and Pt) and their respective nitrogen vacancy complexes in the Ti3N2 MXene monolayer as candidate material for hydrogen evolution reaction (HER). We found that the transition metal dopant atoms as well as transition metal vacancy will feasibly form. However, the cation transition metal dopant atoms with nitrogen vacancy complexes and nitrogen vacancy are endothermic except for the PtTi + VN complex, thus would require additional energy to be realized. To evaluate for the HER activity, the Gibbs free energy and adsorption energetics were calculated. We found that the H atom stably bind to the considered surface configurations. However, the Gibbs free energy is far from optimal for the dopant complexes and the pristine Ti3N2 MXene monolayer. All the considered configurations have magnetic metallic ground state with possible application as 2D magnetic system.

MnCo2S4 – MXene: A novel hybrid electrode material for high performance long-life asymmetric supercapattery

The supercapattery, an ideal electrochemical energy storage device, which can deliver high energy like battery and high power like supercapacitor. Transition metal sulphides’ energy storage capabilities have unfurled beyond the realm of ruthenium and manganese-based oxides by the versatile affordable sulphospinel transition metal sulphides such as MnCo2S4 (MCS). The advancement of synergistic nano-architectures of these transition metal sulphides with two-dimensional MXene material adulated the conductivity and highly reversible redox nature. The hybrid MCS-MXene was synthesised through facile cost effective hydrothermal method and the material were characterised using basic X-Ray Diffraction (XRD) to advanced tools as like electron energy loss spectroscopy (EELS). The electrochemical results depict that the supercapattery electrode of 2D synergistic MCS-MXene hybrid architectures shows highly improved specific capacitance of 600 C/g at 1 A/g current density than pristine MXene and MCS. The fabricated asymmetric supercapattery using hybrid MCS-MXene and bio-derived activated carbon (AC) shows a high specific energy and power density of 25.6 Wh/kg and 6400 W/kg, respectively with excellent cycling stability of 100% capacitance retention after 12,000 cycles.

Effect of atomic vacancy on the electronic and optical properties, quantum capacitance of Zr2CO2-based electrodes

Density functional theory calculation is used to investigate the effect of atomic vacancy on stability, electronic and optical properties, quantum capacitance and surface charge storage of pristine and vacancy-defected Zr2CO2 MXenes. The introduction of O vacancy results in the decrease of band gap, while the introduction of C and Zr vacancies results in the semiconductor-metal transition. The introduction of Zr vacancy results in the appearance of magnetism, which is contributed by O-py, O-px, C-pz, Zr-dz2, Zr-dyz states. The analysis of optical properties indicates that the introduction of the vacancy can make the absorption spectra of the systems more sensitive to the infrared light, and reflectivity is improved, especially in the infrared region. For asymmetric supercapacitor, pristine Zr2CO2 MXene with Zr vacancy can be considered as the potential cathode material, while pristine Zr2CO2 MXenes with C and O vacancy are potential anode materials through the analysis of quantum capacitance and surface charge storage. The increase mechanism of quantum capacitance is further explored through the analysis of density of states.

MXene-Based Nanocomposite Sensors.

The excellent conductivity and versatile surface chemistry of MXenes render these nanomaterials attractive for sensor applications. This mini-review puts recent advances in MXene-based sensors into perspective and provides prospects for the area. It describes the attractive properties and the working principles of MXene-based sensors fabricated from a MXene/polymer nanocomposite or a pristine MXene. The importance of surface modification of MXenes to improve their affinity for polymers and to develop self-healing and durable sensors is delineated. Several novel sensor fabrication methods and their challenges are discussed. Emerging applications of MXene-based sensors including moisture, motion, gas, and humidity detection as well as pressure distribution mapping are critically reviewed. Potential applications of MXene-based sensors in the food industry to monitor food materials and production plants are highlighted.

Assembling Co3O4 Nanoparticles into MXene with Enhanced electrochemical performance for advanced asymmetric supercapacitors

MXenes with unique 2D open structure, large surface-area-to-volume ratios, high pseudo-capacitance, and conductivity are attractive for advanced supercapacitor electrodes. However, the restacking issue of MXenes hinders ion accessibility, resulting in the reduction of volume performance, mass load, and speed capability. To address these issues, a facile hydrothermal synthesis strategy is proposed to fabricate Co3O4 nanoparticles-MXene (Co-MXene) composite by the self-assembly process. Co3O4 nanoparticles, introduced in the MXene matrix, effectively prevent self-restacking and shorten ion/electron transport paths. Consequently, the obtained Co-MXene electrode delivers the high-performance of 1081F g−1 at a current density of 0.5 A g−1, surpassing the pristine MXene electrode (89F g−1 at 0.5 A g−1). Being assembled into asymmetric supercapacitors (ASC), a high energy density of 26.06 Wh kg−1 at 700 W kg−1 was realized. After 8000 cycles, the ASC device maintains 83% of initial specific capacitance at 2 A g−1. This work highlights a simple and efficient method for developing high-performance MXene-based electrodes for supercapacitors.

Stable Ti3C2Tx MXene-Boron Nitride Membranes with Low Internal Resistance for Enhanced Salinity Gradient Energy Harvesting.

Extracting salinity gradient energy through a nanomembrane is an efficient way to obtain clean and renewable energy. However, the membranes with undesirable properties, such as low stability, high internal resistance, and low selectivity, would limit the output performance. Herein, we report two-dimensional (2D) laminar nanochannels in the hybrid Ti3C2Tx MXene/boron nitride (MXBN) membrane with excellent stability and reduced internal resistance for enhanced salinity gradient energy harvesting. The internal resistance of the MXBN membrane is significantly reduced after adding BN in a pristine MXene membrane, due to the small size and high surface charge density of BN nanosheets. The output power density of the MXBN membrane with 44 wt % BN nanosheets reaches 2.3 W/m2, almost twice that of a pristine MXene membrane. Besides, the output power density can be further increased to 6.2 W/m2 at 336 K and stabilizes for 10 h at 321 K, revealing excellent structure stability of the membrane in long-term aqueous conditions. This work presents a feasible method for improving the channel properties, which provides 2D layered composite membranes in ion transport, energy extraction, and other nanofluidic applications.

MXene-CNT/PANI ternary material with excellent supercapacitive performance driven by synergy

• A simple method has been successfully applied to the preparation of MXene-CNT/PANI ternary composite. • MXene makes the CNT/PANI disperse uniformly, achieving good electrical conductivity and facile ion diffusion pathway. • MXene-CNT/PANI electrode has superior gravimetric capacity and cyclic stability. MXene is considered a promising two-dimensional (2D) material with excellent conductivity, and it has been proved to be a potential material for supercapacitor electrode. However, the supercapacitive performances of the pristine MXene are always not satisfactory due to the innate re-stacking tendency of the MXene nanosheets. In this work, the carbon nanotubes/polyaniline (CNT/PANI) nanocomposite was introduced and obtained MXene-CNT/PANI ternary composite electrode. Thanks to the synergy between each component, MXene-CNT/PANI exhibited enhanced specific capacitance that reached 429.4 F/g at 1A/g, which is completely better than that of any single compound in the ternary material. Besides, this ternary composite electrode holds a high stable cycle performance with over 93% retention after 10,000 cycles. Furthermore, a quantitative analysis was also carried out to prove the relationship between the capacitive contribution and the scan rate of the MXene-CNT/PANI.

Meissner to ferromagnetic phase transition in La-decorated functionalized Nb2C MXene: an experimental and computational analysis

This work reports experimental and computational magnetic phase transition from superconducting-diamagnet to ferromagnet in lanthanum (La)-doped functionalized Nb2C MXene. Co-precipitation method is used to synthesize La-doped Nb2C MXene. Structure and morphology of the compound are studied through x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and energy dispersion spectroscopy, confirming the successful doping of La while retaining the two-dimensional (2D) structure of MXene. The magnetic properties of doped sample are studied using field-cooled and zero-field-cooled curves as well as from magnetization (M) versus applied magnetic field (H) graphs. Contrary to the superconductivity-like diamagnetic behavior in pristine Nb2C MXene, the La-doped MXene converts the diamagnetism into the ferromagnetic (FM) phases at all temperatures. The ferromagnetism arises due to the pinning of magnetic spins pinned by Lanthanum itself. The computational analysis of pristine Nb2C MXene confirms its diamagnetic behavior and further clarifies the role of La and functional groups (O and F) in the reduction of diamagnetic behavior in La-doped Nb2C MXene while inducing FM nature. This work provides an interesting superconducting-diamagnetic to FM transition with a possibility of its implementation in 2D spintronics.

Mixed-dimensional heterostructure of few-layer MXene based vertical aligned MoS2 nanosheets for enhanced supercapacitor performance

Herein, a mixed-dimensional heterostructure of MoS2 deposited few-layer Ti3C2Tx nanosheets was synthesized to enhance the supercapacitor performance of pristine 2H phase MoS2 and Ti3C2Tx MXene. Through a facile hydrothermal method, with the introduction of MXene, MoS2 vertically aligns on the surface of few-layer Ti3C2Tx nanosheets and forms an interconnected network structure, which helps to increase the specific surface area of electrode material and improve the accessibility of electrolyte. Meanwhile, metallic Ti3C2Tx nanosheets serve as a highly conductive and stable matrix for MoS2 to grow on, incredibly accelerate the electron transfer and alleviate the aggregation of 2H–MoS2, thus bringing with an electrochemical performance improvement. The MoS2–Ti3C2Tx heterostructure shows a great enhancement in supercapacitor performance, which delivers a remarkable specific capacitance of 303.8 F g−1 at the current density of 1 A g−1, about 5 times of 2H phase MoS2 (62.8 F g−1) and 3 times of Ti3C2Tx (105.8 F g−1). Meanwhile, MoS2–Ti3C2Tx heterostructure electrode exhibits excellent cycling stability, which achieves a high capacitance retention up to 82% even after 10,000 cycles. After being assembled to a symmetric supercapacitor, a specific capacitance of 115.2 F g−1 at 0.5 A g−1 was achieved with good Coulombic efficiency (over 90%) and cycling stability (72.3% of capacitance retention after 10,000 cycles). Meanwhile, MoS2–Ti3C2Tx exhibits a high energy density of 5.1 Wh kg−1 at power density of 298 W kg−1, showing excellent SC performance. This study can provide an archetype of constructing mixed-dimensional heterostructure for synergistically integrating the advantages of different materials and enhancing the electrochemical performance.

In-situ formation of tribofilm with Ti3C2Tx MXene nanoflakes triggers macroscale superlubricity

In the present work, a robust macroscale superlubricity state was achieved with a coefficient of friction (COF) of 0.002 by introducing Ti3C2Tx MXene nanoflakes in glycerol at Si3N4/sapphire interfaces. The MXene-glycerol solution results in the reduction of COF by 96.90% and 97.87% compared to those of pristine glycerol and Ti3C2Tx MXene solutions, respectively. The friction reduction of MXene-glycerol is attributed to the in-situ formation of tribofilm containing Ti3C2Tx MXene nanoflakes and tribochemical layer with Ti3C2Tx MXene on friction pairs, leading to the reduction of shear stress and wear between surface asperities. The synergistic effect between Ti3C2Tx MXene and glycerol enhanced the lubrication performance of Ti3C2Tx MXene, triggering liquid-superlubricity at the macroscale.