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Red phosphorus (RP) with a high theoretical specific capacity (2596 mA h g -1 ) and a moderate lithiation potential (∼0.7 V vs Li + /Li) holds promise as an anode material for lithium-ion batteries (LIBs), which still confronts discernible challenges, including low electrical conductivity, substantial volumetric expansion of 300%, and the shuttle effect induced by soluble lithium polyphosphide (Li x PP s ). Here, S-NRP@Ti 3 C 2 T x composites were in situ prepared through a phosphorus-amine-based method, wherein S-doped red phosphorus nanoparticles (S-NRP) grew and anchored on the crumpled Ti 3 C 2 T x nanosheets via Ti-O-P bonds, constructing a three-dimensional porous structure which provides fast channels for ion and electron transport and effectively buffers the volume expansion of RP. Interestingly, based on the results of adsorption experiments of polyphosphate and DFT calculation, Ti 3 C 2 T x with abundant oxygen functional groups delivers a strong chemical adsorption effect on Li x PP s , thus suppressing the shuttle effect and reducing irreversible capacity loss. Furthermore, S-doping improved the conductivity of red phosphorus nanoparticles, facilitating Li-P redox kinetics. Hence, the S-NRP@Ti 3 C 2 T x anode demonstrates outstanding rate performance (1824 and 1090 mA h g -1 at 0.2 and 4.0 A g -1 , respectively) and superior cycling performance (1401 mAh g -1 after 500 cycles at 2.0 A g -1 ).

Zinc-ion batteries (ZIBs) are promising candidates for safe energy storage applications. However, undesirable parasitic reactions such as dendrite growth, gas evaluation, anode corrosion, and structural damage to the cathode under an acidic microenvironment severely affected cell performance. To resolve these issues, an MXene entrapped in an ionic liquid semi-solid gel polymer electrolyte (GPE) composite was explored. The molecular-level mixing of poly(vinylidene fluoride- co -hexafluoropropylene) (PVHF), zinc trifluoromethanesulfonate (Zn(OTF) 2 ), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF 4 ) ionic liquid, and Ti 3 C 2 T x MXene provided a controlled Zn 2+ shuttle toward the anode/cathode. Ti 3 C 2 T x /EMIBF 4 /Zn(OTF) 2 /PVHF exhibited a breaking strength of 0.36 MPa with an associated extension of 23%. The Zn//Ti 3 C 2 T x /EMIBF 4 /Zn(OTF) 2 /PVHF//Zn symmetric cell with continuous zinc plating/stripping exhibited excellent Zn 2+ ion mobility toward the anode and cathode without undesired reactions. This was confirmed by post-mortem analysis after a symmetric cell compatibility test. The as-prepared GPE with a Na 3 V 2 (PO 4 ) 3 (NVP) cathode exhibited a high chemical diffusion coefficient of 1.14 × 10 -7 . It also showed an outstanding reversible capacity of 89 mAh g -1 at C/10 with an average discharge plateau voltage of 1.45 V, cycle durability, and controlled self-discharge. These results suggested that the Zn 2+ ions in the Ti 3 C 2 T x /EMIBF 4 /Zn(OTF) 2 /PVHF composite are reversibly labile in the anode and cathode directions.

Due to its affordable cost, excellent redox capability, and relatively effective resistance to corrosion in alkaline environments, spinel Co 3 O 4 demonstrates potential as a viable alternative to noble-metal-based electrocatalysts. Nevertheless, these materials continue to exhibit drawbacks, such as limited active surface area and inadequate intrinsic conductivity. Researchers have been trying to increase the electrical conductivity of Co 3 O 4 nanostructures by integrating them with various conductive substrates due to the low conductivity of pristine Co 3 O 4 . In this study, uniform cobalt glycerate solid spheres are first synthesized as the precursor and subsequently transformed into cobalt oxide microspheres by a simple annealing procedure. Co 3 O 4 grown on the surface of Ti 3 C 2 T x -MXene nanosheets (Co 3 O 4 /MXene) was successfully synthesized through electrostatic attraction. In order to create a positively charged surface, the Co 3 O 4 microspheres were treated with aminopropyltriethoxysilane. The Co 3 O 4 /MXene exhibited a low overpotential of 118 mV at 10 mA cm -2 and a Tafel slope of 113 mV dec -1 for the hydrogen evolution reaction, which is much lower than the pristine Co 3 O 4 at 232 and 195.3 mV dec -1 .

Early secretory antigenic target-6 (ESAT-6) is regarded as the most immunogenic protein produced by Mycobacterium tuberculosis , whose detection is of great clinical significance for tuberculosis diagnosis. However, the detection of the ESAT-6 antigen has been hampered by the expensive cost and complex experimental procedures, resulting in low sensitivity. Herein, we developed a titanium carbide (Ti 3 C 2 T x )-based aptasensor for ESAT-6 detection utilizing a triple-signal amplification strategy. First, acetylene black (AB) was immobilized on Ti 3 C 2 T x through a cross-linking reaction to form the Ti 3 C 2 T x -AB-PAn nanocomposite. Meanwhile, AB served as a conductive bridge, and Ti 3 C 2 T x can synergistically promote the electron transfer of PAn. Ti 3 C 2 T x -AB-PAn exhibited outstanding conductivity, high electrochemical signals, and abundant sites for the loading of ESAT-6 binding aptamer II (EBA II) to form a novel signal tag. Second, N-CNTs were adsorbed on NiMn layered double hydride (NiMn LDH) nanoflowers to obtain NiMn LDH/N-CNTs, exhibiting excellent conductivity and preeminent stability to be used as electrode modification materials. Third, the biotinylated EBA (EBA I) was immobilized onto a streptavidin-coated sensing interface, forming an amplification platform for further signal enhancement. More importantly, as a result of the synergistic effect of the triple-signal amplification platform, the aptasensor exhibited a wide detection linear range from 10 fg mL -1 to 100 ng mL -1 and a detection limit of 4.07 fg mL -1 for ESAT-6. We envision that our aptasensor provides a way for the detection of ESAT-6 to assist in the diagnosis of tuberculosis.

MXene is a highly latent capacity electrode material for supercapacitors, but its capacity limits its development. Herein, we have constructed an independently cross-linked three-dimensional (3D) Ti 3 C 2 T X MXene film (Zn-A-MXene) with a hydroxylation surface through a zinc ion (Zn 2+ ) and NaOH. The alkalization of NaOH is used to replace the -F functional group that is not conducive to electrochemical reactions and cross-link the MXene nanosheets through the electrostatic interaction of zinc ions. The synergistic effect can greatly improve the effective area of the electrode, the accessibility of the electrolyte, and the specific capacitance. The 3D Zn-A-MXene films exhibit an extremely high capacity (465.1 F g -1 at 1 A g -1 ). The all-solid-state flexible supercapacitor assembled using a 3D Zn-A-MXene thin film also has a high energy density of 9.55 Wh kg at a power density of 603.16 W kg. After 5000 cycles, the flexible supercapacitor still has 81.25% of its initial capacity, demonstrating good cycling stability. This work furnishes the innovative idea for constructing high-capacity MXene flexible supercapacitors.

Nanozymes with high activity and stability have emerged as a potential alternative to natural enzymes in the past years, but the relationship between the electronic metal-support interactions (EMSI) and catalytic performance in nanozymes still remains unclear. Herein, a copper nanoparticle nanozyme supported on N-doped Ti 3 C 2 T x (Cu NPs@N-Ti 3 C 2 T x ) is successfully synthesized and the modulation of EMSI is achieved by introducing N species. The stronger EMSI between Cu NPs and Ti 3 C 2 T x , involving electronic transfer and an interface effect, is revealed by X-ray photoelectron spectroscopy, soft X-ray absorption spectroscopy, and hard X-ray absorption fine spectroscopy at the atomic level. Consequently, Cu NPs@N-Ti 3 C 2 T x nanozyme exhibits remarkable peroxidase-like activity, surpassing its counterpart (Cu NPs, Ti 3 C 2 T x , Cu NPs-Ti 3 C 2 T x ), suggesting that EMSI significantly enhances catalytic performance. Benefiting from the excellent performance, the colorimetric platform based on Cu NPs@N-Ti 3 C 2 T x nanozyme for detecting astaxanthin is constructed and shows a wide linear detection range of 0.01-50 μM and a limit of detection of 0.015 μM in the sunscreens. Density functional theory is further conducted to reveal that the excellent performance is ascribed to the stronger EMSI. This work opens an avenue for studying the influence of EMSI toward catalytic performance of nanozyme.

As electronic equipment develops rapidly, higher requirements are placed on electrochemical energy-storage devices. These requirements can be met by a lithium-sulfur (Li-S) battery since it has an impressive energy density of 2600 Wh kg -1 and a high theoretical specific capacity of 1675 mAh g -1 . Pitifully, the sluggish redox reaction kinetics and the shuttle effect of polysulfide seriously limit its applications. Separator modification has been proven to be an effective strategy for improving the performance of Li-S batteries. Herein, we have designed a competent three-dimensional separator. It is obtained by embedding Co 3 Se 4 nanoparticles on nitrogen-doped porous carbon (Co 3 Se 4 @N-C) by high-temperature selenization of ZIF-67, which are compounded with Ti 3 C 2 T x by electrostatic dispersion self-assembly, and the compound is used to adjust the surface properties of a polypropylene (PP) separator. Due to the synergistic effect of the superior catalytic performance of Co 3 Se 4 @N-C and the enhancement of adsorption and conductivity bestowed by Ti 3 C 2 T x , lithium-sulfur batteries perform excellently with the modified PP separator. Specifically, the battery with a Co 3 Se 4 @N-C/Ti 3 C 2 T x -modified PP separator exhibits an outstanding rate performance of 787 mAh g -1 at 4C, and stable performance is maintained after 300 cycles at 2C. The density functional theory (DFT) calculations are also performed to confirm the synergistic effect of Co 3 Se 4 @N-C and Ti 3 C 2 T x . This design integrates the merits of catalysis and adsorption and provides a new method for constructing high-performance lithium-sulfur batteries.

Solar energy, as renewable energy, has paid extensive attention for solar thermal utilization due to its unique characteristics such as rich resources, easy access, clean, and pollution-free. Among them, solar thermal utilization is the most extensive one. Nanofluid-based direct absorption solar collectors (DASCs), as an important alternative method, can further improve the solar thermal efficiency. Notably, the stability of photothermal conversion materials and flowing media is critical to the performance of DASC. Herein, we first proposed novel Ti 3 C 2 T x -IL-based nanofluids by the electrostatic interaction, which consists of functional Ti 3 C 2 T x modified with PDA and PEI as a photothermal conversion material and ionic liquid with low viscosity as the flow medium. Ti 3 C 2 T x -IL-based nanofluids exhibit excellent cycle stability, wide spectrum, and efficient solar energy absorption performance. Besides, Ti 3 C 2 T x -IL-based nanofluids maintain liquid state in a range of -80 to 200 °C, and its viscosity was as low as 0.3 Pa·s at 0 °C. Moreover, the equilibrium temperature of Ti 3 C 2 T x @PDA-IL at a very low mass fraction of 0.04% reached 73.9 °C under 1 Sun, indicating an excellent photothermal conversion performance. Furthermore, the application of nanofluids in photosensitive inks has been preliminarily explored, which is expected to play a role in the fields of injectable biomedical materials and photo/electric double-generation thermal and hydrophobic anti ice coatings.

Ti 3 C 2 T x MXene, a two-dimensional transition metal carbide, has attracted substantial interest due to its unique physical properties and a wide range of potential applications. Although the properties of devices using MXene have been substantially enhanced in recent years, it is not fully understood how the oxygen concentration in Ti 3 AlC 2 MAX affects oxide formation in Ti 3 C 2 -based MXene nanosheets and their fundamental properties. To this end, we compared two types of MAX phases: MAX with low oxygen content (LO-MAX) and MAX synthesized by a conventional process. Since the conventional MAX synthesis employs metal (Ti) as a primary material, it is referred to as metal-based MAX (MB-MAX) from here. The oxygen content of the LO-MAX was only 0.56 wt %, which was about 20% compared to that of MAX synthesized using conventional methods. We compared the properties of MXene nanosheets prepared from the LO-MAX with MXene nanosheets obtained from the MB-MAX. Microscopic and chemical analyses revealed smooth and wrinkle-free morphology and small amounts of oxygen in MXene nanosheets prepared from LO-MAX (LO-MXene). The LO-MXene nanosheet film exhibited an exceptionally high conductivity of 10,540 S/cm and an ultralow surface roughness of 1.7 nm, which originated from inhibited surface oxide formation. Moreover, the inhibition of oxide formation strengthened the function of -O or -OH groups on the surface of MXene, thereby facilitating strong hydrogen bonding to the polymer with hydroxyl groups. To clearly reveal these properties, we prepared a pressure sensor by coating these MXene nanosheets on nylon/polyester fibers. The fabricated sensor exhibited a high sensitivity of up to 85.6/kPa and excellent stretch stability and reliability. These results clearly revealed that lowering the oxygen content in MAX can make a decisive contribution to improving the fundamental properties of MXene nanosheets prepared therefrom.

Cost-effective and high-performance H 2 S sensors are required for human health and environmental monitoring. 2D transition-metal carbides and nitrides (MXenes) are appealing candidates for gas sensing due to good conductivity and abundant surface functional groups but have been studied primarily for detecting NH 3 and VOCs, with generally positive responses that are not highly selective to the target gases. Here, we report on a negative response of pristine Ti 3 C 2 T x thin films for H 2 S gas sensing (in contrast to the other tested gases) and further optimization of the sensor performance using a composite of Ti 3 C 2 T x flakes and conjugated polymers (poly[3,6-diamino-10-methylacridinium chloride- co -3,6-diaminoacridine-squaraine], PDS-Cl) with polar charged nitrogen. The composite, preserving the high selectivity of pristine Ti 3 C 2 T x , exhibits an H 2 S sensing response of 2% at 5 ppm (a thirtyfold sensing enhancement) and a low limit of detection of 500 ppb. In addition, our density functional theory calculations indicate that the mixture of MXene surface functional groups needs to be taken into account to describe the sensing mechanism and the selectivity of the sensor in agreement with the experimental results. Thus, this report extends the application range of MXene-based composites to H 2 S sensors and deepens the understanding of their gas sensing mechanisms.

As the most studied two-dimensional (2D) material from the MXene family, Ti 3 C 2 T x has constantly gained interest from academia and industry. Ti 3 C 2 T x MXene has the highest electrical conductivity (up to 24,000 S cm -1 ) and one of the highest stiffness values with a Young's modulus of ∼ 334 GPa among water-dispersible conductive 2D materials. The negative surface charge of MXene helps to disperse it well in aqueous and other polar solvents. This solubility across a wide range of solvents, excellent interface interaction, tunable surface functionality, and stability with other organic/polymeric materials combined with the layered structure of Ti 3 C 2 T x MXene make it a promising material for anticorrosion coatings. While there are many reviews on Ti 3 C 2 T x MXene polymer composites for catalysis, flexible electronics, and energy storage, to our knowledge, no review has been published yet on MXenes' anticorrosion applications. In this brief report, we summarize the current progress and the development of Ti 3 C 2 T x polymer composites for anticorrosion. We also provide an outlook and discussion on possible ways to improve the exploitation of Ti 3 C 2 T x polymer composites as anticorrosive materials. Finally, we provide a perspective beyond Ti 3 C 2 T x MXene composition for the development of future anticorrosion coatings.

Bacterial infection is seriously threatening human health, and the design of high-efficiency and good biocompatibility antibacterial agents is an urgent problem to be solved. However, with the emergence of drug-resistant bacteria, the existing antibacterial agents have low killing efficiency, and the formation of biofilms has further weakened the therapeutic effect. Herein, we constructed an efficient antibacterial system mediated by near-infrared light for synergistic antibacterial and biofilm dissipation. Specifically, the ZnO/Ti 3 C 2 T x with heterojunction was synthesized by hydrothermal growth of ZnO on the surface of lamellar Ti 3 C 2 T x -MXene. The prepared ZnO/Ti 3 C 2 T x had better photothermal ability than ZnO and Ti 3 C 2 T x , respectively. The local thermal effect can not only destroy the integrity of the bacterial membrane but also promote the release of Zn 2+ ions and further improve the antibacterial performance. ZnO/Ti 3 C 2 T x achieved a 100% sterilization rate (better than either ZnO or Ti 3 C 2 T x ) at 150 μg mL -1 . The biofilm dissipation experiment further proved its excellent biofilm ablation effect. More importantly, the results of in vitro cell culture and animal experiments have demonstrated its good biological safety. In summary, this new type of nanomaterial shows strong local chemical photothermal sterilization ability and has great potential to replace traditional antibacterial agents.

Due to its unique high conductivity and flexibility, the two-dimensional MXene material (Ti 3 C 2 T x ) is expected to possess great potential in the thermoelectric field. However, the low thermoelectric performance from high thermal conductivity and a low Seebeck coefficient has limited its practical application. In this report, we demonstrate the uniform growth of ZnO layers on the laminar Ti 3 C 2 T x membrane by atomic layer deposition (ALD). Benefiting from the low-temperature deposition characteristics of the ALD technique, the ZnO@Ti 3 C 2 T x composite films maintain the basic apparent morphology of the original films after the deposition. We reveal that the Schottky barrier formed between ZnO and Ti 3 C 2 T x exhibits an energy-filtering effect, significantly enhancing the Seebeck coefficient to result in more than a double increase in the power factor. Meanwhile, the strong phonon-interface scattering between ZnO and Ti 3 C 2 T x is found to reduce the thermal conductivity of the composite films by a factor of four as compared to pure Ti 3 C 2 T x ones, further improving the overall thermoelectric properties of the ZnO@Ti 3 C 2 T x composite films. Our investigation provides an ALD-based strategy for growing wide band gap layers on the narrow band gap films to improve the thermoelectric performance of various MXene materials.

Developing economical and efficient catalyst for hydrogen generation from ammonia borane (AB) hydrolysis is still a huge challenge. As an alternative strategy, the functional group regulation of metal nanoparticles (NPs)-based catalysts is believed to be capable of improving the catalytic activity. Herein, a series of Ni/Ti 3 C 2 T x -Y (T x = F, -OH; Y denotes etching time (d)) catalysts are synthesized and show remarkably enhanced catalytic activity on the hydrolysis of AB in contrast to the corresponding without regulating. The optimized Ni/Ti 3 C 2 T x -4 with a turnover frequency (TOF) value of 161.0 min -1 exhibits the highest catalytic activity among the non-noble monometallic-based catalyst. Experimental results and theory calculations demonstrate that the excellent catalytic activity benefits from the bimolecular activation channels formed by Ni NPs and Ti 3 C 2 T x -Y. H 2 O and AB molecules are activated simultaneously in the bimolecular activation tunnel. Bimolecular activation reduces the activation energy of AB hydrolysis, and hydrogen generation rate is promoted. This article provides a new approach to design effective catalysts and further supports the bimolecular activation model for the hydrolysis of AB.

Designing sulfur host materials with unique functions such as physical constraint or chemical catalysis to suppress the shuttle effect and promote the fast conversion of polysulfides is a prerequisite for lithium-sulfur batteries (LSBs). Herein, we construct hollow Co(OH) 2 nanotubes connected by Ti 3 C 2 T x nanosheets (denoted as Co(OH) 2 @Ti 3 C 2 T x ) as host materials for sulfur through a simple self-assembly method at room temperature. The large void spaces of Co(OH) 2 nanotubes not only confine higher sulfur loading but also mitigate the volumetric expansion in the process of lithiation. Moreover, the conductive Ti 3 C 2 T x layers facilitate fast electron transfer and catalyze the transition of sulfur based on the terminations on the surface. Combining those two materials can also act as an efficient polysulfide anchor to enable outstanding electrochemical performance. The Co(OH) 2 @Ti 3 C 2 T x @S cathode presents a high discharge capacity of 1400 mAh g -1 at 0.1C and long-cycling stability at 1C for 500 cycles. Moreover, the obtained capacity of Li 2 S precipitation and the dissolution capacity reach 193.3 and 291.1 mAh g -1 , respectively. Consequently, this work demonstrates a facile strategy to design multifunctional materials that effectively confine the polysulfides and enhance the performance of LSBs.

Hard carbon (HC) has attracted considerable attention in the application of sodium-ion battery (SIB) anodes, but the poor realistic capacity and low rate performance severely hinder their practical application. Herein we report a solvent mechanochemical protocol for the in situ fabrication of the HC-MXene/TiO 2 electrode by functionalizing MXene to improve the electrochemical performance of the batteries. MXene (Ti 3 C 2 T x ) with abundant oxygen-containing functional groups reacts with HC particles in the ball milling process to form a Ti-O-C covalent cross-linked HC-MXene composite, in which the edge of the MXene nanosheets is in situ oxidized by air to form TiO 2 nanorods, forming a regular 1D/2D MXene/TiO 2 heterojunction structure. Ti-O-C covalent bonding can protect the heterojunction structures from pulverization and detachment from the current collector during charge/discharge cycles due to sodium-ion intercalation/detachment, thus improving the stability of the electrode structure. Meanwhile, the MXene/TiO 2 heterojunction can form a 3D conductive network and provide more active sites. The resulting HC-MXene/TiO 2 electrode exhibits superior electrode capacity (660 mAh g -1 ), making it a promising anode material for SIBs. This simple and efficient method for preparing MXene/TiO 2 heterojunction-decorated HC provides a new perspective on the structural design of MXene and carbon material composites for SIBs.

Photothermally assisted superhydrophobic sponges play a vital role in the fields of waste oil collection, oil purification, and solar desalination. However, the widely reported superhydrophobic sponges with photothermal efficiency usually suffer from a post-/premodification process of harmful materials, high loading content of photothermal agents, and low photothermal efficiency. Herein, an MXene-based melamine sponge (MS) was facilely fabricated by hydrogen bonding interaction between the amino groups on the skeleton of the MS and the polar groups on the surface of the as-exfoliated 2D MXene Ti 3 C 2 T x nanosheets. Interestingly, the as-fabricated MXene sponge exhibits excellent hydrophobicity and high photothermal efficiency under an extremely low loading of MXene Ti 3 C 2 T x nanosheets (0.1 wt %). Moreover, the highly hydrophobic sponge also possesses a high oil absorption capacity as high as 176 times of its own weight and keeps stable under multiple absorption/desorption cycling tests. Surprisingly, the surface temperature of the MXene sponge can quickly reach 47 °C under illumination and has good reproducibility during multiple light on/off cycles. The excellent photothermal performance and large oil absorption capacity of the MXene sponge endow the highly hydrophobic sponge with fast solvent evaporation speed and high-purity waste oil collection (99.7 wt % dichloromethane) under illumination, which holds great promise for oil/water separation, leaked oil collection, and photo-driven waste oil collection and purification applications. It is envisioned that this work can open a new strategy for new designs of 3D multifunctional sponges for high-performance waste oil collection and purification.

This study highlights the facet structure control of regular Ni x Co 3- x O 4 nanoplates and interfacial modulation through elemental doping and morphologically fitted assembly of Ti 3 C 2 T x nanosheets for high performances in OER/HER and overall water splitting. Over the resulting Ni 0.09 Co 2.91 O 4 /Ti 3 C 2 T x -HT in a solution of 1 M KOH, the OER and HER overpotentials of 262 and 210 mV, respectively, are achievable at a current density of 10 mA cm -2 . In the case of the overall water splitting by using Ni 0.09 Co 2.91 O 4 /Ti 3 C 2 T x -HT as anode and cathode catalysts, only a potential of 1.66 V is needed to obtain a current density of 10 mA cm -2 , and the catalysts can stand for a period of 70 h, remarkably outperforming the RuO 2 -Pt/C-based catalyst and benefiting from the intensive association and interfacial function between the Ti 3 C 2 T x and Ni x Co 3- x O 4 nanosheets. Interestingly, a surface reconstruction from the (112) to (111) facet structure occurred upon the fine-tuned Ni doping of regular Ni x Co 3- x O 4 hexagonal nanoplates and led to a highly active catalyst surface. At x = 0.09, the amount of Ni 3+ becomes the highest, which is favorable for the generation of the critical OH intermediates on Ni x Co 3- x O 4 /Ti 3 C 2 T x -HT. The current study documented the significance of the well-controlled interfacial assembly of transition-metal oxide/MXenes as an effective electrocatalyst in the OER/HER and overall water splitting processes and provided the insights into the structure-performance correlation over such kinds of precious metal-free catalysts.

Recently, the two-dimensional material Ti 3 C 2 T x MXene has attracted interest from researchers in perovskite solar cells (PSCs) with its great advantages in terms of high transmittance, high conductivity, tunable work function, and solution processability. However, the MXene-based PSC performance has still been inferior to that of the traditional TiO 2 - or SnO 2 -based counterpart up until now. Some critical issues regarding to the MXene/perovskite interface still have not been well addressed. Herein, we used the Ti 3 C 2 T x MXene as electron transport layer in PSCs via a room-temperature solution process followed by oxygen plasma treatment. Various characterization techniques were taken to establish the correlation between the surface properties and termination groups of MXene. We showed that oxygen plasma treatment could break parts of Ti-C bonds and generate abundant Ti-O bonds randomly distributed on MXene. The surface modification resulted in tunable work functions of MXene, as well as reduced trap states and improved electron transport close to the interface. In addition, the surface tension of MXene and corresponding perovskite morphology were thoroughly investigated by the contact angle and topography measurements. High-resolution XPS spectra indicated the Pb-O interactions between perovskite and MXene, which contributed to the device stability improvement.

MXenes, a large family of two-dimensional (2D) early transition metal carbides and nitrides, have excellent electrical and electrochemical properties, which can also be explored in assemblies with other 2D materials, like graphene and transition metal dichalcogenides (TMDs), creating heterostructures with unique properties. Understanding the interaction mechanism between 2D materials is critical for the design and manipulation of these 2D heterostructures. Our previous work investigated the interaction between SiO 2 and two MXenes (Ti 3 C 2 T x and Ti 2 CT x ). However, no experimental research has been done on MXene interlayer interactions and interactions in MXene heterostructures. Here, we used atomic force microscopy (AFM) with SiO 2 tip and Ti 3 C 2 T x and Ti 2 CT x MXene-coated tips, respectively, to measure the adhesion energies of graphene, MoSe 2 , Ti 3 C 2 T x , and Ti 2 CT x MXene with other 2D materials. The measured adhesion energies show that only the interfaces involving graphene demonstrate dependence on the number of material monolayers in a stack. Comparing 40 interacting pairs of 2D materials, the lowest adhesion energy (∼0.27 J/m 2 ) was found for the interfaces involving MoSe 2 and the highest adhesion energy was observed for the interfaces involving Ti 3 C 2 T x (∼1.23 J/m 2 ). The obtained set of experimental data for 2D interfaces involving MXenes provides a basis for a future in-depth understanding of adhesive mechanisms at interfaces between 2D materials, which is an important topic for the design of 2D heterostructures with controlled interfacial strength and properties.

Assembling Ti 3 C 2 T x MXene nanosheets into three-dimensional (3D) architecture with controllable alignment is of great importance for electromagnetic wave absorption (EMA) application. However, it is a great challenge to realize it due to the weak van der Waals interconnection between MXene nanosheets. Herein, we propose to introduce gelatin molecules as a "chemical glue" to fabricate the 3D Mxene@gelatin (M@G) nanocomposite aerogel using a unidirectional freeze casting method. The Ti 3 C 2 T x MXene nanosheets are well aligned in the M@G nanocomposite aerogel, yielding much enhanced yet anisotropic mechanical properties. Due to the unidirectional aligned microstructure, the M@G nanocomposite aerogel shows significantly anisotropic EMA properties. M@G-45 shows a -59.5 dB minimum reflection loss (RL min ) at 14.04 GHz together with a 6.24 GHz effective absorption bandwidth in the parallel direction (relative to the direction of unidirectional freeze casting). However, in the vertical direction of the same M@G aerogel, RL min is shifted to a much lower frequency (4.08 GHz) and the effective absorption bandwidth decreases to 0.86 GHz. The anisotropic electromagnetic energy dissipation mechanism was deeply investigated, and the impendence match plays a critical role for electromagnetic wave penetration. Our lightweight M@G nanocomposite aerogel with controllable MXene alignment is very promising in EMA application.

Excellent comprehensive dielectric properties (including dielectric constant and loss) are essential for electromechanical transducers. This work introduced a bimodal network composite with poly(dimethyl siloxane) (PDMS) and delaminated Ti 3 C 2 T x sheets ( d -Ti 3 C 2 T x ) modified with hyperbranched polysiloxane (HPSi) (referred to as HPSi- d -Ti 3 C 2 T x ). Before the final cross-linking, HPSi- d -Ti 3 C 2 T x , trapped with short-chain PDMS (C S -PDMS) and long-chain PDMS (C L -PDMS), was pre-reacted, which formed a distinct bimodal network structure. d -Ti 3 C 2 T x /PDMS and HPSi- d -Ti 3 C 2 T x /PDMS composites with different filler loadings were prepared, and their percolation thresholds ( f c ) were 1.32 and 1.43 vol %, respectively The dielectric constant of 1.40 vol % HPSi- d -Ti 3 C 2 T x /PDMS is 23.7 at 10 2 Hz, which is 1.5 times that of 1.28 vol % d -Ti 3 C 2 T x /PDMS and 8.5 times that of pure PDMS. Meanwhile, the dielectric loss of HPSi- d -Ti 3 C 2 T x /PDMS composite is still relatively small (0.11 at 10 3 Hz). The origin of dielectric property optimization of the composite is attributed to the boundary capacitor model, the accumulated charges at the interfaces between the conductive filler and the insulating polymer matrix of the composite, and the distinct bimodal network structure.

Ti 3 C 2 T x (MXene) exhibits attractive properties in different applications. However, traditional synthesis leads to unsatisfactory yield of two-dimensional (2D) Ti 3 C 2 T x , e.g., lower than 20%, which stems from the strong interactions of potential Ti-Ti bonds and residual Ti-Al bonds between the adjacent Ti 3 C 2 layers, hindering the effective intercalation and delamination. Herein, we propose a facile hydrothermal-assisted intercalation (HAI) strategy to boost the yield of 2D sheets, achieving a record high value of 74%. This HAI assists the diffusion and intercalation of reagent effectively, promoting the subsequent delamination; meanwhile, an antioxidant is applied to protect these Ti 3 C 2 T x from oxidation during the HAI process. Therefore, massive Ti 3 C 2 T x 2D sheets can be easily synthesized. Thanks to the synergistic effect of high conductivity and substantial terminated functionalities, these Ti 3 C 2 T x 2D sheets show promising application in supercapacitor, providing a high capacitance of 482 F g -1 . Besides, the ultrafast carrier dynamics results of Ti 3 C 2 T x 2D sheets clearly imply the promising application in photocatalysis due to the relatively long bleaching relaxation time. Our work not only paves the way for the mass production of Ti 3 C 2 T x 2D sheets but also provides insights into their electronic and optical properties.

Wearable gas sensors have received lots of attention for diagnostic and monitoring applications, and two-dimensional (2D) materials can provide a promising platform for fabricating gas sensors that can operate at room temperature. In the present study, the room temperature gas-sensing performance of Ti 3 C 2 T x nanosheets was investigated. 2D Ti 3 C 2 T x (MXene) sheets were synthesized by removal of Al atoms from Ti 3 AlC 2 (MAX phases) and were integrated on flexible polyimide platforms with a simple solution casting method. The Ti 3 C 2 T x sensors successfully measured ethanol, methanol, acetone, and ammonia gas at room temperature and showed a p-type sensing behavior. The fabricated sensors showed their highest and lowest response toward ammonia and acetone gas, respectively. The limit of detection of acetone gas was theoretically calculated to be about 9.27 ppm, presenting better performance compared to other 2D material-based sensors. The sensing mechanism was proposed in terms of the interactions between the majority charge carriers of Ti 3 C 2 T x and gas species.

Lithium-sulfur batteries have attracted increasing attention as one of the most promising candidates for next-generation energy storage systems. However, the poor cycling performance and the low utilization of sulfur greatly hinder its practical applications. Here we report the improved performance of lithium-sulfur batteries by coating Ti 3 C 2 T x MXene nanosheets (where T stands for the surface termination, such as -O, -OH, and/or -F) on commercial "Celgard" membrane. In favor of the ultrathin two-dimensional structure, the Ti 3 C 2 T x MXene can form a uniform coating layer with a minimum mass loading of 0.1 mg cm -2 and a thickness of only 522 nm. Owing to the improved electric conductivity and the effective trapping of polysulfides, the lithium-sulfur batteries with MXene-functionalized separators exhibit superior performance including high specific capacities and cycling stability.

Ti3C2Tx, a 2D titanium carbide in the MXenes family, is obtained from Ti3AlC2 through selective etching of the Al layer. Due to its good conductivity and high volumetric capacitance, Ti3C2Tx is regarded as a promising candidate for supercapacitors. In this paper, the fabrication of Ti3C2Tx/RGO composites with different proportions of Ti3C2Tx and RGO is reported, in which RGO acts as a conductive "bridge" to connect different Ti3C2Tx blocks and a matrix to alleviate the volume change during charge/discharge process. In addition, RGO nanosheets can serve as a second nanoscale current collector and support as well for the electrode. The electrochemical performance of the as-fabricated Ti3C2Tx/RGO electrodes, characterized by CV, GCD, and EIS, are also reported. A highest specific capacitance (Cs) of 154.3 F/g at 2 A/g is obtained at the Ti3C2Tx: RGO weight ratio of 7:1 combined with an outstanding capacity retention (124.7 F/g) after 6000 cycles at 4 A/g.