Few-layered Ti3C2Tx Research Articles

High-performance and freestanding PPy/Ti3C2Tx composite film for flexible all-solid-state supercapacitors

To utilize the flexibility and high theoretical specific capacitance of polypyrrole (PPy) and high electrical conductivity and moderate electrochemical properties of emerging two-dimensional materials, MXene, herein, a high performance, flexible, and freestanding PPy/Ti3C2Tx (a kind of MXene) composite film electrode is prepared by vacuum-assisted filtration of single- and few-layer Ti3C2Tx sheets to obtain a Ti3C2Tx film and then electrochemically deposition of PPy on the film. High-resolution scanning and transmission electron microscope (HRSTEM) observations of the focused ion beam prepared sample reveal that the electrode possesses a unique microstructure: PPy not only polymerizes on the surface of the Ti3C2Tx film, but also intercalates into the gaps within the film. An optimized sample shows an outstanding specific capacitance of 420.2 F g−1 at 1 A g−1, a remarkable cycling stability of 86% capacitance retention after 10,000 cycles, a distinguished flexibility and a good mechanical performance, owing to the special microstructure and synergistic effect of the PPy and Ti3C2Tx. A symmetric all-solid-state flexible supercapacitor fabricated by the 400PPy175/Ti3C2Tx electrode exhibits remarkable specific capacitance of 258.3 F g−1 at 0.5 A g−1, a superior energy density of 10.82 μWh·mg−1 at a power density of 0.11 mW mg−1, and an outstanding power density of 1.89 mW mg−1 at 3.99 μWh·mg−1, indicating that the PPy/Ti3C2Tx film has great potential as supercapacitor electrode.

Two-Dimensional Titanium Carbide (Ti3C2Tx) MXenes of Different Flake Sizes Studied by Scanning Electrochemical Microscopy in Different Electrolytes

Two-dimensional (2D) layered materials are studied in efforts to discover new compounds and for their fascinating properties engendered by their sheet-like structure and tunable surfaces. MXenes are an emergent class of layered, synthesized transition metal carbides and carbonitrides that are useful in addressing the formidable challenges of sensing at the energy-water nexus. This work reports systematic structural and electrochemical properties of titanium carbide (Ti3C2Tx) MXenes revealed by varying interlayer spacing, flake thickness and lateral size under different electrolytes. In addition to traditional electrode kinetics, we utilized surface sensitive scanning electrochemical microscopy (SECM) to gain a more complete understanding of rich MXene surface chemistry and corresponding knowledge about the physicochemical processes, including inherent electrochemistry and heterogeneous charge transfer characteristics, at electrode/electrolyte (solid/liquid) interfaces. We employed electron microscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, x-ray diffraction, and Raman spectroscopy to determine surface morphology, microscopic and electronic structure and lattice vibrational properties. It is shown that Ti3C2Tx or, specifically, transition metal Ti, undergoes irreversible oxidation and lithiation in a positive potential window, which strongly depends on the flake thickness and type (aqueous versus organic) of the electrolyte. Multi-layered and smaller Ti3C2Tx flakes exhibit faster electron transfer kinetics (kET = 1.2 cm s−1) with a potassium ferrocyanide [Fe(CN)6]4−/3− redox probe, compared to few-layered Ti3C2Tx (kET = 0.3 cm s−1) in aqueous and organic electrolyte (kET = 4.9 cm s−1) with a [Fe(CN)6]4−/3− redox probe, and compared to a few-layered Ti3C2Tx (kET = 0.9 cm s−1). In addition, the few-layered free standing Ti3C2Tx film electrode remains intact following irreversible oxidation. These properties help to establish structure–property-electroactivity relationships among different types of Ti3C2Tx MXenes.

Partial Atomic Tin Nanocomplex Pillared Few-Layered Ti3C2Tx MXenes for Superior Lithium-Ion Storage

HighlightsA facile NH4+ method was proposed to prepare Sn nanocomplex pillared few-layered Ti3C2Tx MXene nanosheets.The MXene nanosheets showed excellent lithium-ion storage performances among MXene-based materials, which can maintain 1016 mAh g−1 after 1200 cycles at 2000 mA g−1 and deliver a stable capacity of 680 mAh g−1 at 5 A g−1.

Embedding few-layer Ti3C2Tx into alkalized g-C3N4 nanosheets for efficient photocatalytic degradation

Solution of the increasingly important problem of aquatic pollution requires the use of an economical, energy-efficient, highly effective and environmentally-friendly catalyst. Polymeric carbon nitride (C3N4) has shown to be a promising metal-free photocatalyst that however suffers from strong charge recombination and poor conductivity, while MXenes have shown to be perfect co-catalysts for the photocatalytic process but show poor stability. In this study, we successfully constructed a robust heterostructure photocatalyst in which few-layer Ti3C2Tx was embedded into alkalized C3N4 without being oxidized. The photocatalyst showed stable and effective photocatalytic performance for the removal of tetracycline hydrochloride and other organic compounds under visible light irradiation. Different characterization methods were used to elucidate the morphology and structure of the as-prepared photocatalyst. The robust heterostructure and the intimate interaction between the two constituents of the composite were verified. Based on the van der Waals heterostructure, Ti3C2Tx acts as the electron acceptor and helps to form Schottky junction, preventing charge recombination of the photocatalyst. And in the meantime, the electrons from C3N4 protect Ti3C2Tx from oxidation. SEM and XRD results demonstrated that the Ti3C2Tx structure remains unchanged after calcination and after photodegradation experiments. Furthermore, a possible mechanism for photocatalytic tetracycline hydrochloride degradation was proposed based on the results of radical scavenging experiments. This work provides a strategy to strengthen heterostructure between 2D materials, and shows that carbon nitride and Mxenes could be promising materials for photocatalytic wastewater pre-treatment applications.

Fast and Universal Solution-Phase Flocculation Strategy for Scalable Synthesis of Various Few-Layered MXene Powders.

MXenes have gained great attention in various fields because of their fascinating properties; however, the preparation of few-layered MXene powders is still limited by serious restacking of MXene nanosheets. Herein, for the first time, we have demonstrated an effective ammonium ion route to fundamentally address restacking and aggregation of the MXene nanosheets, using a solution-phase flocculation method (NH4+ method and modified NH4+ method) for large-scale preparation of few-layered Ti3C2Tx MXene powders in large quantities. The as-prepared few-layered MXene nanosheet powders show large size in the ab plane without the restacking phenomenon even at scanning electron microscopy measurements of 400× magnification, demonstrating the effectiveness of the proposed method. The method is also suitable for large-scale synthesis of other few-layered MXene powders, including Nb4C3Tx, V2CTx, Nb2CTx, etc., providing a general approach for the preparation of various few-layered MXene nanosheet powders, which represents a significant result for the development of MXenes.

Few-layer Ti3C2T MXene delaminated via flash freezing for high-rate electrochemical capacitive energy storage

Abstract Few-layer Ti3C2Tx MXene is synthesized from multi-layered Ti3C2Tx via a flash freezing-assisted delamination process. During the flash freezing process, the water molecules in the interlayers of multi-layered MXene are induced to rearrange and produce volume expansion, thus notably expand the MXenes’ interlayer distance to form few-layer MXene. The synthesized few-layer Ti3C2Tx MXene nanosheets display a very small thickness (less than 5 Ti3C2 atom-layers) and expanded interlayer spacing. Consequently, the few-layer Ti3C2Tx exhibits enhanced capacitance (255 F g−1 vs. 177 F g−1 for the multi-layered Ti3C2Tx) and significantly optimized rate capability (150 F g−1 at 200 mV s−1 vs. 25 F g−1 for the multi-layered Ti3C2Tx), because redox-active sites in the few-layer MXene are easily accessible to electrolyte ions. Moreover, an asymmetric supercapacitor is constructed using the few-layer Ti3C2Tx negative electrode and an activated carbon fiber positive electrode. The asymmetric supercapacitor presents a high energy density of 17.9 Wh kg−1 and a high power density of 14 kW kg−1, which is inseparable from its wide voltage window of 1.4 V and the good rate performance of the few-layer Ti3C2Tx MXene electrode. Overall, the flash freezing-assist delamination provides an effective and environmental-friendly strategy to synthesize few-layer MXene materials for high-rate electrochemical energy storage.

2D Ti3C2Tx MXene/aramid nanofibers composite films prepared via a simple filtration method with excellent mechanical and electromagnetic interference shielding properties

Electromagnetic shielding (EMI) materials are becoming more and more important because of the increasingly serious radiation pollution. The preparation of high mechanical strength, ultrathin, lightweight, flexible materials with excellent EMI shielding performance have so far been elusive. Here, we try to prepare an ultrathin, lightweight and flexible film with excellent EMI shielding performance using one-dimensional aramid nanofibers (ANFs) and two-dimensional few-layered Ti3C2Tx through a simple filtration method. The ultimate tensile strength and strain of the film are up to 116.71 MPa and 2.64%. The EMI shielding effectiveness and the specific EMI shielding efficiency are 34.71 dB and 21971.37 dB cm2 g−1, which will be no recession after 1000 times bending. Our results show that a practical EMI shielding material with excellent performances has been successfully prepared, which will be widely applied in wearable electronics, robot joints, and precision instrument protection and so on.

Fabrication and investigation on the ultra-thin and flexible Ti3C2Tx/co-doped polyaniline electromagnetic interference shielding composite films

Polyaniline (PANI) was co-doped using dodecylbenzenesulfonic acid (DBSA) and hydrochloric acid (HCl), and few-layered Ti3C2Tx was prepared via ionic intercalation followed by sonication-assisted method. Then the Ti3C2Tx/co-doped PANI (Ti3C2Tx/c-PANI) electromagnetic interference (EMI) shielding composite films were prepared by vacuum assisted filtration. FTIR, XPS, XRD, and Raman indicated that c-PANI was successfully synthesized. XRD, SEM, AFM, and TEM revealed the successful preparation of few-layered Ti3C2Tx. The electrical conductivity, EMI shielding effectiveness (EMI SE), and tensile strength of the Ti3C2Tx/c-PANI EMI shielding composite films were all increased with increasing the mass fraction of Ti3C2Tx. When the mass ratio of Ti3C2Tx to c-PANI was 7:1, the thickness of Ti3C2Tx/c-PANI composite film was only 40 μm. And the corresponding electrical conductivity, EMI SE, and tensile strength were significantly enhanced to 24.4 S/cm, 36 dB, and 19.9 MPa, which were 81, 2.3, and 7.7 times those of pure c-PANI film (0.3 S/cm, 16 dB, and 2.6 MPa), respectively. Our fabricated Ti3C2Tx/c-PANI EMI shielding composite films present potential applications in the high-tech fields with demand for ultrathin, lightweight, and flexible EMI shielding materials.

3D Ti3C2Tx MXene/C hybrid foam/epoxy nanocomposites with superior electromagnetic interference shielding performances and robust mechanical properties

Few-layered Ti3C2Tx MXene was prepared by ionic intercalation and sonication-assisted method. Porous three-dimensional (3D) Ti3C2Tx MXene/C hybrid foam (MCF) was fabricated by sol-gel followed by thermal reduction. The MCF/epoxy EMI shielding nanocomposites were obtained via vacuum-assisted impregnation followed by curing process. When the mass fraction of MCF was 4.25 wt% (MCF-5), the MCF-5/epoxy EMI shielding nanocomposites exhibited the optimal electrical conductivity of 184 S/m and the maximum EMI SE of 46 dB, 3.1 × 104 and 4.8 times higher than that of MCF-0/epoxy nanocomposites (without Ti3C2Tx MXene), respectively. Furthermore, the corresponding Young's modulus of 3.96 GPa and hardness of 0.31 GPa was increased by 13% and 11%, respectively. Conductive networks can realize the attenuation and dissipation of electromagnetic waves by multiple reflection & reabsorption, and absorption is main shielding mechanism. Unique 3D conductive networks of MCF would expand wider application of the Ti3C2Tx MXene/polymer-based nanocomposites in high-tech EMI shielding fields.

Fabrication on the annealed Ti3C2Tx MXene/Epoxy nanocomposites for electromagnetic interference shielding application

Few-layered Ti3C2Tx MXene was fabricated by ionic intercalation and sonication-assisted method, followed by thermal reduction at medium-low temperature. Then annealed Ti3C2Tx/epoxy electromagnetic interference (EMI) shielding nanocomposites were obtained by solution casting method. XRD, SEM, AFM and TEM indicated the successful preparation of few-layered Ti3C2Tx. FTIR, XPS and XRD showed that thermal reduction removed partial polar groups on the surface of Ti3C2Tx with no by-product. For a fixed Ti3C2Tx loading, compared with Ti3C2Tx/epoxy EMI shielding nanocomposites, the annealed Ti3C2Tx/epoxy EMI shielding nanocomposites exhibited relatively higher electrical conductivity and excellent EMI shielding effectiveness (SE). When the mass fraction of annealed Ti3C2Tx was 15 wt%, the annealed Ti3C2Tx/epoxy EMI shielding nanocomposites presented the optimal electrical conductivity of 105 S/m and EMI SE of 41 dB, 176% and 37% higher than that of 15 wt% Ti3C2Tx/epoxy EMI shielding nanocomposites. Furthermore, the 5 wt% annealed Ti3C2Tx/epoxy EMI shielding nanocomposites exhibited the optimal Young's modulus of 4.32 GPa and hardness of 0.29 GPa, respectively.

Few-layer MXene Ti3C2Tx (T = F, O, or OH) saturable absorber for visible bulk laser

The novel two-dimensional MXenes have been investigated in the photonics field in areas such as broadband nonlinearity, pulse laser generation and passive photonic diode, and so on. In this contribution, the nonlinear optical response at the visible band and the demand pulse laser generation based on MXenes was initially realized. The few-layer MXene Ti3C2Tx was fabricated and utilized as a saturable absorber (SA) to realize passive Q-switched visible bulk laser covering the spectral range of orange (607 nm), red (639 nm), and deep red (721 nm). At the three wavelength, the maximum average output powers and the shortest pulse widths were (111 mW, 426 ns) for 607 nm, (150 mW, 264 ns) for 639 nm, (115 mW, 328 ns) for 721 nm, respectively. Our experimental results indicate the MXene Ti3C2Tx SA could be an efficient and promising optical modulator in the visible domain.

Few-layered Ti3C2Tx MXenes coupled with Fe2O3 nanorod arrays grown on carbon cloth as anodes for flexible asymmetric supercapacitors

Few-layered Ti3C2Tx MXene wrapped Fe2O3 nanorod arrays grown on carbon cloth, is a promising anode for high-performance flexible asymmetric supercapacitor.

Surface modified MXene film as flexible electrode with ultrahigh volumetric capacitance

In recent years, the rapid development of portable equipment and flexible wearable devices urgently requires supercapacitor electrode material with high volumetric capacitance. Ti3C2Tx, a member of MXenes family, is one of the most promising supercapacitor electrode material candidates. However, how to further enhance the volumetric capacitance of the Ti3C2Tx is still a great challenge at present. In this paper, a simple and eco-friendly method is presented by preparing flexible Ti3C2Tx supercapacitor electrode using self-assembly of few-layer Ti3C2Tx followed by alkalinizing and annealing treatment. The alkalinized and annealed Ti3C2Tx film (denoted as ak-Ti3C2Tx film-A) exhibits an ultrahigh volumetric capacitance of 1805 F cm−3 at 1 A g−1, and an impressive cycling stability up to 98% capacitance retention after 8000 cycles. The significant improvement in volumetric capacitance performance is mainly due to the increase of redox-active sites exposed by removal of surface terminal groups during alkalinizing and annealing, and the enhancement in conductivity of the film owing to the annealing induced increase of crystalline order. Moreover, the supercapacitor fabricated with ak-Ti3C2Tx film-A displays an outstanding volumetric energy density of 45.2 Wh L−1. This work provides a new strategy for design and development of other MXenes-based materials with high volumetric capacitance performance for flexible and highly integrated supercapacitors.

Fabrication of high-performance MXene-based all-solid-state flexible microsupercapacitor based on a facile scratch method

MXenes have emerged as promising electrode materials for microsupercapacitors (MSCs) owing to their high volumetric and areal capacitances. In addition to the development of novel electrode materials, fabrication of interdigital electrodes is another key to realize high-performance MSCs. Herein, we demonstrate the patterning of few-layered Ti3C2Tx nanosheets on various substrates for MSCs by a facile, fast, and nearly zero-cost ‘scratch’ strategy. The fabricated Ti3C2Tx-based all-solid-state MSC achieves a high areal capacitance of 25.5 mF cm−2, which benefits from the unique layered structure and high electrical conductivity of the electrode. The fabricated planar MSC also delivers good cycling stability and excellent flexibility. Moreover, our fabrication strategy can be readily extended to other composite films for MSCs and become potential micropower sources for miniaturized electronic devices.

Few-layer Ti3C2Tx MXene: A promising surface plasmon resonance biosensing material to enhance the sensitivity

In this contribution, a novel surface plasmon resonance (SPR) biosensor with few-layer Ti3C2Tx MXene to enhance the sensitivity is proposed. Few-layer Ti3C2Tx MXene is coated on the surface of metals thin film to act as a protective layer and further to improve the sensitivity. The results show that the sensitivity enhancements at λ = 633 nm are 16.8%, 28.4%, 46.3% and 33.6% for the proposed SPR biosensors based on Au with 4 layers Ti3C2Tx, Ag with 7 layers Ti3C2Tx, Al with 12 layers Ti3C2Tx and Cu with 9 layers Ti3C2Tx, respectively. Moreover, we have discussed the sensitivity of the proposed Au-based SPR biosensor with monolayer Ti3C2Tx MXene works at λ = 532 nm, the result shows that the sensitivity can reach 224.5°/RIU. Our contributions reveal potential applications of few-layer Ti3C2Tx MXene as a new type of biosensing material, and it is therefore anticipated that Ti3C2Tx MXene and other 2D MXene nanomaterials could find promising applications in SPR biosensors.

Atomic Defects in Monolayer Titanium Carbide (Ti3C2Tx) MXene.

The 2D transition metal carbides or nitrides, or MXenes, are emerging as a group of materials showing great promise in lithium ion batteries and supercapacitors. Until now, characterization and properties of single-layer MXenes have been scarcely reported. Here, using scanning transmission electron microscopy, we determined the atomic structure of freestanding monolayer Ti3C2Tx flakes prepared via the minimally intensive layer delamination method and characterized different point defects that are prevalent in the monolayer flakes. We determine that the Ti vacancy concentration can be controlled by the etchant concentration during preparation. Density function theory-based calculations confirm the defect structures and predict that the defects can influence the surface morphology and termination groups, but do not strongly influence the metallic conductivity. Using devices fabricated from single- and few-layer Ti3C2Tx MXene flakes, the effect of the number of layers in the flake on conductivity has been demonstrated.

Antibacterial Activity of Ti₃C₂Tx MXene.

MXenes are a family of atomically thin, two-dimensional (2D) transition metal carbides and carbonitrides with many attractive properties. Two-dimensional Ti3C2Tx (MXene) has been recently explored for applications in water desalination/purification membranes. A major success indicator for any water treatment membrane is the resistance to biofouling. To validate this and to understand better the health and environmental impacts of the new 2D carbides, we investigated the antibacterial properties of single- and few-layer Ti3C2Tx MXene flakes in colloidal solution. The antibacterial properties of Ti3C2Tx were tested against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) by using bacterial growth curves based on optical densities (OD) and colonies growth on agar nutritive plates. Ti3C2Tx shows a higher antibacterial efficiency toward both Gram-negative E. coli and Gram-positive B. subtilis compared with graphene oxide (GO), which has been widely reported as an antibacterial agent. Concentration dependent antibacterial activity was observed and more than 98% bacterial cell viability loss was found at 200 μg/mL Ti3C2Tx for both bacterial cells within 4 h of exposure, as confirmed by colony forming unit (CFU) and regrowth curve. Antibacterial mechanism investigation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with lactate dehydrogenase (LDH) release assay indicated the damage to the cell membrane, which resulted in release of cytoplasmic materials from the bacterial cells. Reactive oxygen species (ROS) dependent and independent stress induction by Ti3C2Tx was investigated in two separate abiotic assays. MXenes are expected to be resistant to biofouling and offer bactericidal properties.