A Laser-Induced Mo2CTx MXene Hybrid Anode for High-Performance Li-Ion Batteries

MXenes, a fast-growing family of two-dimensional (2D) transition metal carbides/nitrides, are promising for electronics and energy storage applications. Mo₂CT_x MXene, in particular, has demonstrated a higher capacity than other MXenes as an anode for Li-ion batteries. Yet, such enhanced capacity is accompanied by slow kinetics and poor cycling stability. Herein, it is revealed that the unstable cycling performance of Mo₂CT_x is attributed to the partial oxidation into MoO_x with structural degradation. A laser-induced Mo₂CT_x/Mo₂C (LS-Mo₂CT_x) hybrid anode has been developed, of which the Mo₂C nanodots boost redox kinetics, and the laser-reduced oxygen content prevents the structural degradation caused by oxidation. Meanwhile, the strong connections between the laser-induced Mo₂C nanodots and Mo₂CT_x nanosheets enhance conductivity and stabilize the structure during charge–discharge cycling. The as-prepared LS-Mo₂CT_x anode exhibits an enhanced capacity of 340 mAh g⁻¹ vs 83 mAh g⁻¹ (for pristine) and an improved cycling stability (capacity retention of 106.2% vs 80.6% for pristine) over 1000 cycles. The laser-induced synthesis approach underlines the potential of MXene-based hybrid materials for high-performance energy storage applications.     

Probing the Domain Architecture in 2D α‐Mo2C via Polarized Raman Spectroscopy

MXenes are emerging 2D materials with intriguing properties such as excellent stability and high conductivity. Here, a systematic study on the Raman spectra of 2D α‐Mo₂C (molybdenum carbide), a promising member in MXene family, is conducted. Six experimentally observed Raman modes from ultrathin α‐Mo₂C crystal are first assigned with the assistance of phonon dispersion calculated from density functional theory. Angle‐resolved polarized Raman spectroscopy indicates the anisotropy of α‐Mo₂C in the b–c plane. Raman spectroscopy is further used to study the unique domain structures of 2D α‐Mo₂C crystals grown by chemical vapor deposition. A Raman mapping investigation suggests that most of the α‐Mo₂C flakes contain multiple domains and the c‐axes of neighboring domains tend to form a 60° or 120° angle, due to the weak Mo? C bonds in this interstitial carbide and the low formation energy of the carbon chains along three equivalent directions. This study demonstrates that polarized Raman spectroscopy is a powerful and effective way to characterize the domain structures in α‐Mo₂C, which will facilitate the further exploration of the domain‐structure‐related properties and potential applications of α‐Mo₂C.     

Assembling 2D MXenes into Highly Stable Pseudocapacitive Electrodes with High Power and Energy Densities

Electrochemical capacitors (ECs) that store charge based on the pseudocapacitive mechanism combine high energy densities with high power densities and rate capabilities. 2D transition metal carbides (MXenes) have been recently introduced as high‐rate pseudocapacitive materials with ultrahigh areal and volumetric capacitances. So far, 20 different MXene compositions have been synthesized and many more are theoretically predicted. However, since most MXenes are chemically unstable in their 2D forms, to date only one MXene composition, Ti₃C₂T_x, has shown stable pseudocapacitive charge storage. Here, a cation‐driven assembly process is demonstrated to fabricate highly stable and flexible multilayered films of V₂CT_x and Ti₂CT_x MXenes from their chemically unstable delaminated single‐layer flakes. The electrochemical performance of electrodes fabricated using assembled V₂CT_x flakes surpasses Ti₃C₂T_x in various aqueous electrolytes. These electrodes show specific capacitances as high as 1315 F cm^?3 and retain ≈77% of their initial capacitance after one million charge/discharge cycles, an unprecedented performance for pseudocapacitive materials. This work opens a new venue for future development of high‐performance supercapacitor electrodes using a variety of 2D materials as building blocks.     

Electrostatically Assembling 2D Nanosheets of MXene and MOF‐Derivatives into 3D Hollow Frameworks for Enhanced Lithium Storage

As an essential member of 2D materials, MXene (e.g., Ti₃C₂T_x) is highly preferred for energy storage owing to a high surface‐to‐volume ratio, shortened ion diffusion pathway, superior electronic conductivity, and neglectable volume change, which are beneficial for electrochemical kinetics. However, the low theoretical capacitance and restacking issues of MXene severely limit its practical application in lithium‐ion batteries (LIBs). Herein, a facile and controllable method is developed to engineer 2D nanosheets of negatively charged MXene and positively charged layered double hydroxides derived from ZIF‐67 polyhedrons into 3D hollow frameworks via electrostatic self‐assembling. After thermal annealing, transition metal oxides (TMOs)@MXene (CoO/Co₂Mo₃O₈@MXene) hollow frameworks are obtained and used as anode materials for LIBs. CoO/Co₂Mo₃O₈ nanosheets prevent MXene from aggregation and contribute remarkable lithium storage capacity, while MXene nanosheets provide a 3D conductive network and mechanical robustness to facilitate rapid charge transfer at the interface, and accommodate the volume expansion of the internal CoO/Co₂Mo₃O₈. Such hollow frameworks present a high reversible capacity of 947.4 mAh g^?1 at 0.1 A g^?1, an impressive rate behavior with 435.8 mAh g^?1 retained at 5 A g^?1, and good stability over 1200 cycles (545 mAh g^?1 at 2 A g^?1).     

Fast Gelation of Ti3C2Tx MXene Initiated by Metal Ions

Gelation is an effective way to realize the self‐assembly of nanomaterials into different macrostructures, and in a typical use, the gelation of graphene oxide (GO) produces various graphene‐based carbon materials with different applications. However, the gelation of MXenes, another important type of 2D materials that have different surface chemistry from GO, is difficult to achieve. Here, the first gelation of MXenes in an aqueous dispersion that is initiated by divalent metal ions is reported, where the strong interaction between these ions and ? OH groups on the MXene surface plays a key role. Typically, Fe²⁺ ions are introduced in the MXene dispersion which destroys the electrostatic repulsion force between the MXene nanosheets in the dispersion and acts as linkers to bond the nanosheets together, forming a 3D MXene network. The obtained hydrogel effectively avoids the restacking of the MXene nanosheets and greatly improves their surface utilization, resulting in a high rate performance when used as a supercapacitor electrode (≈226 F g^?1 at 1 V s^?1). It is believed that the gelation of MXenes indicates a new way to build various tunable MXene‐based structures and develop different applications.     

Strong Surface‐Bound Sulfur in Carbon Nanotube Bridged Hierarchical Mo2C‐Based MXene Nanosheets for Lithium–Sulfur Batteries

In this work, hydroxyl‐functionalized Mo₂C‐based MXene nanosheets are synthesized by facilely removing the Sn layer of Mo₂SnC. The hydroxyl‐functionalized surface of Mo₂C suppresses the shuttle effect of lithium polysulfides (LiPSs) through strong interaction between Mo atoms on the MXenes surface and LiPSs. Carbon nanotubes (CNTs) are further introduced into Mo₂C phase to enlarge the specific surface area of the composite, improve its electronic conductivity, and alleviate the volume change during discharging/charging. The strong surface‐bound sulfur in the hierarchical Mo₂C‐CNTs host can lead to a superior electrochemical performance in lithium–sulfur batteries. A large reversible capacity of ≈925 mAh g ^{? 1} is observed after 250 cycles at a current density of 0.1 C (1 C = 1675 mAh g^?1) with good rate capability. Notably, the electrodes with high loading amounts of sulfur can also deliver good electrochemical performances, i.e., initial reversible capacities of ≈1314 mAh g^?1 (2.4 mAh cm^?2), ≈1068 mAh g^?1 (3.7 mAh cm^?2), and ≈959 mAh g^?1 (5.3 mAh cm^?2) at various areal loading amounts of sulfur (1.8, 3.5, and 5.6 mg cm^?2) are also observed, respectively.     

In Situ Growth of MAPbBr3 Nanocrystals on Few‐Layer MXene Nanosheets with Efficient Energy Transfer

The performance of perovskite nanocrystals (NCs) in optoelectronics and photocatalysis is severely limited by the presence of large amounts of crystal boundaries in NCs film that greatly restricts energy transfer. Creating heterostructures based on perovskite NCs and 2D materials is a common approach to improve the energy transport at the perovskite/2D materials interface. Herein, methylamine lead bromide (MAPbBr₃, MA: CH₃NH₃⁺) perovskite NCs are homogeneously deposited on highly conductive few‐layer MXene (Ti₃C₂T_x) nanosheets to form heterostructures through an in situ solution growth method. An optimal mixed solvent ratio is essential to realize the growth of perovskite NCs on Ti₃C₂T_x nanosheets. Time‐resolved photoluminescence spectroscopy, transient absorption spectroscopy, and the photoresponse of electron‐ and hole‐only photoelectric conversion devices reveal the interfacial energy transfer behavior within MAPbBr₃/Ti₃C₂T_x heterostructures. The present investigation may provide a useful guide toward use of halide perovskite/2D material heterostructures in applications such as photocatalysis as well as optoelectronics.     

Saturable Absorption in 2D Ti3C2 MXene Thin Films for Passive Photonic Diodes

MXenes comprise a new class of 2D transition metal carbides, nitrides, and carbonitrides that exhibit unique light–matter interactions. Recently, 2D Ti₃CNT_x (T_x represents functional groups such as ? OH and ? F) was found to exhibit nonlinear saturable absorption (SA) or increased transmittance at higher light fluences, which is useful for mode locking in fiber‐based femtosecond lasers. However, the fundamental origin and thickness dependence of SA behavior in MXenes remain to be understood. 2D Ti₃C₂T_x thin films of different thicknesses are fabricated using an interfacial film formation technique to systematically study their nonlinear optical properties. Using the open aperture Z‐scan method, it is found that the SA behavior in Ti₃C₂T_x MXene arises from plasmon‐induced increase in the ground state absorption at photon energies above the threshold for free carrier oscillations. The saturation fluence and modulation depth of Ti₃C₂T_x MXene is observed to be dependent on the film thickness. Unlike other 2D materials, Ti₃C₂T_x is found to show higher threshold for light‐induced damage with up to 50% increase in nonlinear transmittance. Lastly, building on the SA behavior of Ti₃C₂T_x MXenes, a Ti₃C₂T_x MXene‐based photonic diode that breaks time‐reversal symmetry to achieve nonreciprocal transmission of nanosecond laser pulses is demonstrated.     

Multifunctional Nanocomposites with High Strength and Capacitance Using 2D MXene and 1D Nanocellulose

The family of two‐dimensional (2D) metal carbides and nitrides, known as MXenes, are among the most promising electrode materials for supercapacitors thanks to their high metal‐like electrical conductivity and surface‐functional‐group‐enabled pseudocapacitance. A major drawback of these materials is, however, the low mechanical strength, which prevents their applications in lightweight, flexible electronics. A strategy of assembling freestanding and mechanically robust MXene (Ti₃C₂T_x ) nanocomposites with one‐dimensional (1D) cellulose nanofibrils (CNFs) from their stable colloidal dispersions is reported. The high aspect ratio of CNF (width of ≈3.5 nm and length reaching tens of micrometers) and their special interactions with MXene enable nanocomposites with high mechanical strength without sacrificing electrochemical performance. CNF loading up to 20%, for example, shows a remarkably high mechanical strength of 341 MPa (an order of magnitude higher than pristine MXene films of 29 MPa) while still maintaining a high capacitance of 298 F g^?1 and a high conductivity of 295 S cm^?1. It is also demonstrated that MXene/CNF hybrid dispersions can be used as inks to print flexible micro‐supercapacitors with precise dimensions. This work paves the way for fabrication of robust multifunctional MXene nanocomposites for printed and lightweight structural devices.     

2D MXene–TiO2 Core–Shell Nanosheets as a Data-Storage Medium in Memory Devices

MXenes, an emerging class of 2D transition metal carbides and nitrides with the general formula M_n+1X_nT_x (n = 1–4), have potential for application as floating gates in memory devices because of their intrinsic properties of a 2D structure, high density-of-states, and high work function. In this study, a series of MXene–TiO₂ core–shell nanosheets are synthesized by deterministic control of the surface oxidation of MXene. The floating gate (multilayer MXene) and tunneling layer (TiO₂) in a nano-floating-gate transistor memory (NFGTM) device are prepared simultaneously by a facile, low-cost, and water-based process. The memory performance is optimized via adjustment of the thickness of the oxidation layer formed on the MXene surface. The fabricated MXene NFGTMs exhibit excellent nonvolatile memory characteristics, including a large memory window (>35.2 V), high programming/erasing current ratio (≈10⁶), low off-current (<1 pA), long retention (>10⁴ s), and cyclic endurance (300 cycles). Furthermore, synaptic functions, including the excitatory postsynaptic current/inhibitory postsynaptic current, paired-pulse facilitation, and synaptic plasticity (long-term potentiation/depression), are successfully emulated using the MXene NFGTMs. The successful control of MXene oxidation and its application to NFGTMs are expected to inspire the application of MXene as a data-storage medium in future memory devices.     

Highly Enhanced Pseudocapacitive Performance of Vanadium‐Doped MXenes in Neutral Electrolytes

2D titanium carbide (Ti₃C₂T_x MXene) is recognized as a promising material for pseudocapacitor electrodes in acidic solutions, while the current studies in neutral electrolytes show much poorer performances. By a simple hydrothermal method, vanadium‐doped Ti₃C₂T_x 2D nanosheets are prepared to tune the interaction between MXene and alkali metal adsorbates (Li⁺, Na⁺, and K⁺) in the neutral electrolyte. Maintaining the 2D morphology of MXene, the coexisting V³⁺ and V⁴⁺ are confirmed to form surface V–C and V–O species. At a medium doping level of V:Ti = 0.17:1, the V‐doped MXene exhibits the highest capacitance of 365.9 F g^?1 in 2 m KCl (10 mV s^?1) and excellent stability (5% loss after 5000 cycles), compared to only 115.7 F g^?1 of pristine MXene. Density functional theory calculations reveal the stronger alkali metal ion–O interaction on V‐doped MXene surface than unmodified MXene and a further capacitance boost to 404.9 F g^?1 using Li⁺‐containing neutral electrolyte is reported, which is comparable to the performance under acidic conditions.     

Ultrasensitive Surface‐Enhanced Raman Spectroscopy Detection Based on Amorphous Molybdenum Oxide Quantum Dots

Surface‐enhanced Raman spectroscopy (SERS) based on plasmonic semiconductive material has been proved to be an efficient tool to detect trace of substances, while the relatively weak plasmon resonance compared with noble metal materials restricts its practical application. Herein, for the first time a facile method to fabricate amorphous H_xMoO₃ quantum dots with tunable plasmon resonance is developed by a controlled oxidization route. The as‐prepared amorphous H_xMoO₃ quantum dots show tunable plasmon resonance in the region of visible and near‐infrared light. Moreover, the tunability induced by SC CO₂ is analyzed by a molecule kinetic theory combined with a molecular thermodynamic model. More importantly, the ultrahigh enhancement factor of amorphous H_xMoO₃ quantum dots detecting on methyl blue can be up to 9.5 × 10⁵ with expending the limit of detection to 10^?9 m . Such a remarkable porperty can also be found in this H_xMoO₃‐based sensor with Rh6G and RhB as probe molecules, suggesting that the amorphous H_xMoO₃ quantum dot is an efficient candidate for SERS on molecule detection in high precision.     

Self‐Assembly of Transition Metal Oxide Nanostructures on MXene Nanosheets for Fast and Stable Lithium Storage

Recently, a new class of 2D materials, i.e., transition metal carbides, nitrides, and carbonitrides known as MXenes, is unveiled with more than 20 types reported one after another. Since they are flexible and conductive, MXenes are expected to compete with graphene and other 2D materials in many applications. Here, a general route is reported to simple self‐assembly of transition metal oxide (TMO) nanostructures, including TiO₂ nanorods and SnO₂ nanowires, on MXene (Ti₃C₂) nanosheets through van der Waals interactions. The MXene nanosheets, acting as the underlying substrate, not only enable reversible electron and ion transport at the interface but also prevent the TMO nanostructures from aggregation during lithiation/delithiation. The TMO nanostructures, in turn, serve as the spacer to prevent the MXene nanosheets from restacking, thus preserving the active areas from being lost. More importantly, they can contribute extraordinary electrochemical properties, offering short lithium diffusion pathways and additional active sites. The resulting TiO₂/MXene and SnO₂/MXene heterostructures exhibit superior high‐rate performance, making them promising high‐power and high‐energy anode materials for lithium‐ion batteries.     

An Ultrafast Conducting Polymer@MXene Positive Electrode with High Volumetric Capacitance for Advanced Asymmetric Supercapacitors

Pseudocapacitors or redox capacitors that synergize the merits of batteries and double‐layer capacitors are among the most promising candidates for high‐energy and high‐power energy storage applications. 2D transition metal carbides (MXenes), an emerging family of pseudocapacitive materials with ultrahigh rate capability and volumetric capacitance, have attracted much interest in recent years. However, MXenes have only been used as negative electrodes as they are easily oxidized at positive (anodic) potential. To construct a high‐performance MXene‐based asymmetric device, a positive electrode with a compatible performance is highly desired. Herein, an ultrafast polyaniline@MXene cathode prepared by casting a homogenous polyaniline layer onto a 3D porous Ti₃C₂T_x MXene is reported, which enables the stable operation of MXene at positive potentials because of the enlarged work function after compositing with polyaniline, according to the first‐principle calculations. The resulting flexible polyaniline@MXene positive electrode demonstrates a high volumetric capacitance of 1632 F cm^?3 and an ultrahigh rate capability with 827 F cm^?3 at 5000 mV s^?1, surpassing all reported positive electrodes. An asymmetric device is further fabricated with MXene as the anode and polyaniline@MXene as the cathode, which delivers a high energy density of 50.6 Wh L^?1 and an ultrahigh power density of 127 kW L^?1.     

Surface Nanopore Engineering of 2D MXenes for Targeted and Synergistic Multitherapies of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common and deadly gastrointestinal malignancies. Given its insensitivity to traditional systematic chemotherapy, new therapeutic strategies for efficient HCCs treatment are urgently needed. Here, the development of a novel 2D MXene‐based composite nanoplatform for highly efficient and synergistic chemotherapy and photothermal hyperthermia against HCC is reported. A surface‐nanopore engineering strategy is developed for the MXenes’ surface functionalization, which achieves the uniform coating of a thin mesoporous‐silica layer onto the surface of 2D Ti₃C₂ MXene (Ti₃C₂@mMSNs). This strategy endows MXenes with well‐defined mesopores for on‐demand drug release/delivery, enhanced hydrophilicity/dispersity, and abundant surface chemistry for targeting engineering. Systematic in vitro and in vivo evaluations have demonstrated the high active‐targeting capability of arginine‐glycine‐aspartic acid (RGD)‐targeting Ti₃C₂@mMSNs into tumor, and the synergistic chemotherapy (contributed by the mesoporous shell) and photothermal hyperthermia (contributed by the Ti₃C₂ MXene core) completely eradicate the tumor without obvious reoccurrence. This work not only provides a novel strategy for efficiently combating HCC by developing MXene‐based composite nanoplatforms, but also paves a new way for extending the biomedical applications of MXenes by surface‐nanopore engineering.     

Recent Advances in Layered Ti3C2Tx MXene for Electrochemical Energy Storage

Ti₃C₂T_x, a typical representative among the emerging family of 2D layered transition metal carbides and/or nitrides referred to as MXenes, has exhibited multiple advantages including metallic conductivity, a plastic layer structure, small band gaps, and the hydrophilic nature of its functionalized surface. As a result, this 2D material is intensively investigated for application in the energy storage field. The composition, morphology and texture, surface chemistry, and structural configuration of Ti₃C₂T_x directly influence its electrochemical performance, e.g., the use of a well‐designed 2D Ti₃C₂T_x as a rechargeable battery anode has significantly enhanced battery performance by providing more chemically active interfaces, shortened ion‐diffusion lengths, and improved in‐plane carrier/charge‐transport kinetics. Some recent progresses of Ti₃C₂T_x MXene are achieved in energy storage. This Review summarizes recent advances in the synthesis and electrochemical energy storage applications of Ti₃C₂T_x MXene including supercapacitors, lithium‐ion batteries, sodium‐ion batteries, and lithium–sulfur batteries. The current opportunities and future challenges of Ti₃C₂T_x MXene are addressed for energy‐storage devices. This Review seeks to provide a rational and in‐depth understanding of the relation between the electrochemical performance and the nanostructural/chemical composition of Ti₃C₂T_x, which will promote the further development of 2D MXenes in energy‐storage applications.     

Oxide Thin‐Film Electronics using All‐MXene Electrical Contacts

2D MXenes have shown great promise in electrochemical and electromagnetic shielding applications. However, their potential use in electronic devices is significantly less explored. The unique combination of metallic conductivity and hydrophilic surface suggests that MXenes can also be promising in electronics and sensing applications. Here, it is shown that metallic Ti₃C₂ MXene with work function of 4.60 eV can make good electrical contact with both zinc oxide (ZnO) and tin monoxide (SnO) semiconductors, with negligible band offsets. Consequently, both n‐type ZnO and p‐type SnO thin‐film transistors (TFTs) have been fabricated entirely using large‐area MXene (Ti₃C₂) electrical contacts, including gate, source, and drain. The n‐ and p‐type TFTs show balanced performance, including field‐effect mobilities of 2.61 and 2.01 cm² V^?1 s^?1 and switching ratios of 3.6 × 10⁶ and 1.1 × 10³, respectively. Further, complementary metal oxide semiconductor (CMOS) inverters are demonstrated. The CMOS inverters show large voltage gain of 80 and excellent noise margin of 3.54 V, which is 70.8% of the ideal value. Moreover, the operation of CMOS inverters is shown to be very stable under a 100 Hz square waveform input. The current results suggest that MXene (Ti₃C₂) can play an important role as contact material in nanoelectronics.     

Tailoring Structure,Composition, and Energy Storage Properties of MXenes from Selective Etching of In‐Plane,Chemically Ordered MAX Phases

The exploration of 2D solids is one of our time's generators of materials discoveries. A recent addition to the 2D world is MXenes that possses a rich chemistry due to the large parent family of MAX phases. Recently, a new type of atomic laminated phases (coined i‐MAX) is reported, in which two different transition metal atoms are ordered in the basal planes. Herein, these i‐MAX phases are used in a new route for tailoriong the MXene structure and composition. By employing different etching protocols to the parent i‐MAX phase (Mo_2/3Y_1/3)₂AlC, the resulting MXene can be either: i) (Mo_2/3Y_1/3)₂C with in‐plane elemental order through selective removal of Al atoms or ii) Mo_1.33C with ordered vacancies through selective removal of both Al and Y atoms. When (Mo_2/3Y_1/3)₂C (ideal stoichiometry) is used as an electrode in a supercapacitor—with KOH electrolyte—a volumetric capacitance exceeding 1500 F cm^?3 is obtained, which is 40% higher than that of its Mo_1.33C counterpart. With H₂SO₄, the trend is reversed, with the latter exhibiting the higher capacitance (≈1200 F cm^?3). This additional ability for structural tailoring will indubitably prove to be a powerful tool in property‐tailoring of 2D materials, as exemplified here for supercapacitors.     

Horizontal Growth of Lithium on Parallelly Aligned MXene Layers towards Dendrite‐Free Metallic Lithium Anodes

Although metallic lithium is an extremely promising anode for lithium‐based batteries due to its high theoretical capacity, the uncontrollable growth of lithium dendrites, in particular under deep stripping and plating, have stagnated its application. It is demonstrated that parallelly aligned MXene (Ti₃C₂T_x ) layers enable the efficient guiding of lithium nucleation and growth on the surface of 2D MXene nanosheets, giving rise to horizontal‐growth lithium anodes. Moreover, the inherent fluorine terminations in MXene afford a uniform and durable solid electrolyte interface with lithium fluoride at the anode/electrolyte interface, efficiently regulating electromigration of lithium ions. Thus, a dendrite‐free lithium anode with a long cycle life up to 900 h and excellent deep stripping–plating capabilities up to 35 mAh cm^?2 is achieved, which can further serve as an anode for a lithium metal battery, exhibiting high cycle stability up to 1000 cycles.     

Theranostic 2D Tantalum Carbide (MXene)

The large‐dimensional and rigid ceramic bulks fabricated by high‐temperature solid‐phase reaction and sintering have never been considered for possibly entering and circulating within the blood vessels for biomedical applications, especially on combating cancer. Here, it is reported for the first time that MAX ceramic biomaterials exhibit unique functionalities for dual‐mode photoacoustic/computed tomography imaging and are highly effective for in vivo photothermal ablation of tumors upon being exfoliated into ultrathin nanosheets within atomic thickness (MXene). As a paradigm, 2D ultrathin tantalum carbide nanosheets (Ta₄C₃ MXenes) with nanosized lateral sizes are successfully synthesized based on a two‐step liquid exfoliation strategy of MAX phase Ta₄AlC₃ by combined hydrofluoric acid (HF) etching and probe sonication. The structural, electronic, and surface characteristics of the as‐exfoliated nanosheets are revealed by various characterizations combined with first‐principles calculations via density functional theory. Especially, the superior photothermal‐conversion performance (efficiency η of 44.7%) and in vitro/in vivo photothermal ablation of tumor by biocompatible soybean phospholipid‐modified Ta₄C₃ nanosheets are systematically revealed and demonstrated. Based on the large family members of MXenes, this work may offer a paradigm that MXenes can achieve the specific biomedical applications (here, theranostic) providing that their compositions and nanostructures are carefully tuned and optimized to meet the strict requirements of biomedicine.