Flexible Carbon Dots-Intercalated MXene Film Electrode with Outstanding Volumetric Performance for Supercapacitors

2D MXenes have emerged as promising supercapacitor electrode materials due to their metallic conductivity, pseudo-capacitive mechanism, and high density. However, layer-restacking is a bottleneck that restrains their ionic kinetics and active site exposure. Herein, a carbon dots-intercalated strategy is proposed to fabricate flexible MXene film electrodes with both large ion-accessible active surfaces and high density through gelation of calcium alginate (CA) within the MXene nanosheets followed by carbonization. The formation of CA hydrogel within the MXene nanosheets accompanied by evaporative drying endow the MXene/CA film with high density. In the carbonization process, the CA-derived carbon dots can intercalate into the MXene nanosheets, increasing the interlayer spacing and promoting the electrolytic diffusion inside the MXene film. Consequently, the carbon dots-intercalated MXene films exhibit high volumetric capacitance (1244.6 F cm⁻³ at 1 A g⁻¹), superior rate capability (662.5 F cm⁻³ at 1000 A g⁻¹), and excellent cycling stability (93.5% capacitance retention after 30 000 cycles) in 3 m H₂SO₄. Additionally, an all-solid-state symmetric supercapacitor based on the carbon dots-intercalated MXene film achieves a high volumetric energy density of 27.2 Wh L⁻¹. This study provides a simple yet efficient strategy to construct high-volumetric performance MXene film electrodes for advanced supercapacitors.     

Scalable 3D Self-Assembly of MXene Films for Flexible Sandwich and Microsized Supercapacitors

The self-assembly of large-area MXene films is the main step to realize their applications in various energy storage devices. However, the scalable self-assembly of flexible thin MXene films with high conductivity as well as excellent mechanical and electrochemical properties is still a challenge. Herein, a synchronous reduction and self-assembly strategy to fabricate flexible MXene films is developed, where MXene films are synchronously reduced and self-assembled on the Zn foil surface. Furthermore, the self-assembly of MXene films can be scaled up by controlling the area of Zn substrates. By adjusting the patterns of Zn substrates, the interdigital MXene patterns can also be obtained via a selectively reducing/assembling process. The resultant MXene films demonstrate high electrical conductivity, large specific surface area, and excellent mechanical properties. Thus they can serve as the electrodes of flexible supercapacitor devices directly. As a proof of concept, flexible sandwich and microsized supercapacitors are designed based on the above MXene film electrodes. Both sandwich and microsized supercapacitors display stable electrochemical performance under various bending states. This study provides a route to achieve large-area MXene-based films or microsized structures for applications in the field of energy storage.     

MXene‐Bonded Flexible Hard Carbon Film as Anode for Stable Na/K‐Ion Storage

Hard carbon (HC) is a promising anode material for sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs), but the volume change during the insertion/extraction of Na⁺ or K⁺ limits the cycle life, especially for PIBs due to the large ion size of K⁺. Moreover, the conventional anodes fabricated through the coating method cannot satisfy the requirement of flexible devices. Here, it is shown that 2D carbide flakes of Ti₃C₂T_x MXene can be used as multifunctional conductive binders for flexible HC electrodes. The use of MXene nanosheets eliminates the need for all the electrochemically inactive components in the conventional polyvinylidene fluoride–bonded HC electrode, including polymer binders, conductive additives, and current collectors. In MXene‐bonded HC electrodes, conductive and hydrophilic MXene 2D nanosheets construct a 3D network, which can effectively stabilize the electrode structure and accommodate the volume expansion of HC during the charge/discharge process, leading to an enhanced electrode capacity and excellent cycle performance as anodes for both SIBs and PIBs. Benefiting from the 3D conductive network, the MXene‐bonded HC film electrodes also present improved rate capability, indicating MXene is a very promising multifunctional binder for next‐generation flexible secondary rechargeable batteries.     

Engineering 3D Ion Transport Channels for Flexible MXene Films with Superior Capacitive Performance

2D MXene materials are of considerable interest for future energy storage. A MXene film could be used as an effective flexible supercapacitor electrode due to its flexibility and, more importantly, its high specific capacitance. However, although it has excellent electronic conductivity, sluggish ionic kinetics within the MXene film becomes a fundamental limitation to the electrochemical performance. To compensate for the relative deficiency, MXene films are frequently reduced to several micrometer dimensions with low mass loading (<1 mg cm^?2), to the point of detriment of areal performance and commercial value. Herein, for the first time, the design of a 3D porous MXene/bacterial cellulose (BC) self‐supporting film is reported for ultrahigh capacitance performance (416 F g^?1, 2084 mF cm^?2) with outstanding mechanical properties and high flexibility, even when the MXene loading reaches 5 mg cm^?2. The highly interconnected MXene/BC network enables both excellent electron and ion transport channel. Additionally, a maximum energy density of 252 µWh cm^?2 is achieved in an asymmetric supercapacitor, higher than that of all ever‐reported MXene‐based supercapacitors. This work exploits a simple route for assembling 2D MXene materials into 3D porous films as state‐of‐the‐art electrodes for high performance energy storage devices.     

Wearable Integrated Self-Powered Electroluminescence Display Device Based on All-In-One MXene Electrode for Information Encryption

Anti-counterfeiting and visual optical information encryption/decryption technology have attracted widespread attention in the field of information security. Luminescent encryption technologies still face a huge challenge in external high voltage power supply, complex architecture, and expensive decryption equipment, which hinder their broad applications. Herein, a wearable integrated self-powered electroluminescent (EL) display device (W-ELD) that consists of MXene/Silicone-based triboelectric nanogenerator (MS-TENG) and EL device based on a shared MXene electrode is developed for patterned display and information encryption. The W-ELD features an all-in-one MXene electrode with excellent flexibility and high conductivity of 0.6 kΩ sq⁻¹, which is shared by both MS-TENG and EL devices. The MS-TENG demonstrates excellent output performances (output power of 0.9 Wm⁻²) and high stability and durability (10⁴ cycles), which can directly light up the flexible patterned EL device. More importantly, when dripping conductive electrolyte solution, the W-ELD based on “中國”-patterned MXene electrode can precisely reveal the encryption information through self-powered EL emission for real-time visualized information interaction. Consequently, the all-in-one MXene electrode-based W-ELD that integrates both MS-TENG and EL device demonstrates exceptional patterned EL-based information encryption features, which offers a potential prospect in wearable self-powered optoelectronic devices, flexible displays, and encryption technology.     

Alternating‐Current MXene Polymer Light‐Emitting Diodes

MXenes (Ti₃C₂) are 2D transition‐metal carbides and carbonitrides with high conductivity and optical transparency. However, transparent MXene electrodes suitable for polymer light‐emitting diodes (PLEDs) have rarely been demonstrated. With the discovery of the excellent electrical stability of MXene under an alternating current (AC), herein, PLEDs that employ MXene electrodes and exhibit high performance under AC operation (AC MXene PLEDs) are presented. The PLED exhibits a turn‐on voltage, current efficiency, and brightness of 2.1 V, 7 cd A^?1, and 12 547 cd m^?2, respectively, when operated under AC with a frequency of 1 kHz. The results indicate that the undesirable electric breakdown associated with heat arising from the poor interface of the MXene with a hole transport layer in the direct‐current mode is efficiently suppressed by the transient injection of carriers accompanied by the alternating change of the electric polarity under the AC, giving rise to reliable light emission with a high efficiency. The solution‐processable MXene electrode can be readily fabricated on a flexible polymer substrate, allowing for the development of a mechanically flexible AC MXene PLED with a higher performance than flexible PLEDs employing solution‐processed nanomaterial‐based electrodes such as carbon nanotubes, reduced graphene oxide, and Ag nanowires.     

A Robust,Freestanding MXene‐Sulfur Conductive Paper for Long‐Lifetime Li–S Batteries

Freestanding, robust electrodes with high capacity and long lifetime are of critical importance to the development of advanced lithium–sulfur (Li–S) batteries for next‐generation electronics, whose potential applications are greatly limited by the lithium polysulfide (LiPS) shuttle effect. Solutions to this issue have mostly focused on the design of cathode hosts with a polar, sulfurphilic, conductive network, or the introduction of an extra layer to suppress LiPS shuttling, which either results in complex fabrication procedures or compromises the mechanical flexibility of the device. A robust Ti₃C₂T_x/S conductive paper combining the excellent conductivity, mechanical strength, and unique chemisorption of LiPSs from MXene nanosheets is reported. Importantly, repeated cycling initiates the in situ formation of a thick sulfate complex layer on the MXene surface, which acts as a protective membrane, effectively suppressing the shuttling of LiPSs and improving the utilization of sulfur. Consequently, the Ti₃C₂T_x/S paper exhibits a high capacity and an ultralow capacity decay rate of 0.014% after 1500 cycles, the lowest value reported for Li–S batteries to date. A robust prototype pouch cell and full cell of Ti₃C₂T_x/S paper // lithium foil and prelithiated germanium are also demonstrated. The preliminary results show that Ti₃C₂T_x/S paper holds great promise for future flexible and wearable electronics.     

Interconnected Metallic Membrane Enabled by MXene Inks Toward High-Rate Anode and High-Voltage Cathode for Li-Ion Batteries

The ever-increasing popularity of smart electronics demands advanced Li-ion batteries capable of charging faster and storing more energy, which in turn stimulates the innovation of electrode additives. Developing single-phase conductive networks featuring excellent mechanical strength/integrity coupled with efficient electron transport and durability at high-voltage operation should maximize the rate capability and energy density, however, this has proven to be quite challenging. Herein, it is shown that a 2D titanium carbide (known as MXene) metallic membrane can be used as single-phase interconnected conductive binder for commercial Li-ion battery anode (i.e., Li₄Ti₅O₁₂) and high-voltage cathodes (i.e., Ni_0.8Mn_0.1Co_0.1O₂). Electrodes are fabricated directly by slurry-casting of MXene aqueous inks composited with active materials without any other additives or solvents. The interconnected metallic MXene membrane ensures fast charge transport and provides good durability, demonstrating excellent rate performance in the Li//Li₄Ti₅O₁₂ cell (90 mAh g⁻¹ at 45 C) and high reversible capacity (154 mAh g⁻¹ at 0.2 C/0.5 C) in Li//Ni_0.8Mn_0.1Co_0.1O₂ cell coupled with high-voltage operation (4.3 V vs Li/Li⁺). The LTO//NMC full cell demonstrates promising cycling stability, maintaining capacity retention of 101.4% after 200 cycles at 4.25 V (vs Li/Li⁺) operation. This work provides insights into the rational design of binder-free electrodes toward acceptable cyclability and high-power density Li-ion batteries.     

Flexible Solid‐State Supercapacitor Based on Graphene‐based Hybrid Films

A flexible solid‐state asymmetric supercapacitor based on bendable film electrodes with 3D expressway‐like architecture of graphenes and “hard nano‐spacer” is fabricated via an extended filtration assisted method. In the designed structure of the positive electrode, graphene sheets are densely packed, and Ni(OH)₂ nanoplates are intercalated in between the densely stacked graphenes. The 3D expressway‐like electrodes exhibit superior supercapacitive performance including high gravimetric capacitance (≈573 F g^‐1), high volumetric capacitance (≈655 F cm^‐3), excellent rate capability, and superior cycling stability. In addition, another hybrid film of graphene and carbon nanotubes (CNT) is fabricated as the negative electrodes for the designed asymmetric device. In the obtained graphene@CNT films, CNTs served as the hard spacer to prevent restacking of graphene sheets but also as a conductive and robust network to facilitate the electrons collection/transport in order to fulfill the demand of high‐rate performance of the asymmetric supercapacitor. Based on these two hybrid electrode films, a solid‐state flexible asymmetric supercapacitor device is assembled, which is able to deliver competitive volumetric capacitance of 58.5 F cm^‐3 and good rate capacity. There is no obvious degradation of the supercapacitor performance when the device is in bending configuration, suggesting the excellent flexibility of the device.     

Inkjet Printing of Self‐Assembled 2D Titanium Carbide and Protein Electrodes for Stimuli‐Responsive Electromagnetic Shielding

2D titanium carbides (MXene) possess significant characteristics including high conductivity and electromagnetic interference shielding efficiency (EMI SE) that are important for applications in printed and flexible electronics. However, MXene‐based ink formulations are yet to be demonstrated for proper inkjet printing of MXene patterns. Here, tandem repeat synthetic proteins based on squid ring teeth (SRT) are employed as templates of molecular self‐assembly to engineer MXene inks that can be printed as stimuli‐responsive electrodes on various substrates including cellulose paper, glass, and flexible polyethylene terephthalate (PET). MXene electrodes printed on PET substrates are able to display electrical conductivity values as high as 1080 ± 175 S cm^?1, which significantly exceeds electrical conductivity values of state‐of‐the‐art inkjet‐printed electrodes composed of other 2D materials including graphene (250 S cm^?1) and reduced graphene oxide (340 S cm^?1). Furthermore, this high electrical conductivity is sustained under excessive bending deformation. These flexible electrodes also exhibit effective EMI SE values reaching 50 dB at films with thicknesses of 1.35 µm, which mainly originate from their high electrical conductivity and layered structure.     

Flexible Transparent Bifunctional Capacitive Sensors with Superior Areal Capacitance and Sensing Capability based on PEDOT:PSS/MXene/Ag Grid Hybrid Electrodes

Flexible transparent supercapacitors (FTSs) have aroused considerable attention. Nonetheless, balancing energy storage capability and transparency remains challenging. Herein, a new type of FTSs with both excellent energy storage and superior transparency is developed based on PEDOT:PSS/MXene/Ag grid ternary hybrid electrodes. The hybrid electrodes can synergistically utilize the high optoelectronic properties of Ag grids, the excellent capacitive performance of MXenes, and the superior chemical stability of PEDOT:PSS, thus, simultaneously demonstrating excellent optoelectronic properties (T: ≈89%, R_s: ≈39 Ω sq⁻¹), high areal specific capacitance, superior mechanical softness, and excellent anti-oxidation capability. Due to the excellent comprehensive performances of the hybrid electrodes, the resulting FTSs exhibit both high optical transparency (≈71% and ≈60%) and large areal specific capacitance (≈3.7 and ≈12 mF cm⁻²) besides superior energy storage capacity (P: 200.93, E: 0.24 µWh cm⁻²). Notably, the FTSs show not only excellent energy storage but also exceptional sensing capability, viable for human activity recognition. This is the first time to achieve FTSs that combine high transparency, excellent energy storage and good sensing all-in-one, which make them stand out from conventional flexible supercapacitors and promising for next-generation smart flexible energy storage devices.     

Intercalation of Metal Ions into Ti3C2Tx MXene Electrodes for High‐Areal‐Capacitance Microsupercapacitors with Neutral Multivalent Electrolytes

Microsupercapacitors (MSCs) with neutral multivalent electrolytes are safer, cheaper, and exhibit higher theoretical energy densities compared with the MSCs with acidic and alkaline electrolytes. Multivalent charge carriers (e.g., Mg²⁺, Zn²⁺) in the MSCs with Ti₃C₂T_x MXene electrodes have not been demonstrated, which could theoretically achieve higher specific capacitances and energy densities. However, because of the larger size of multivalent charge carriers, the MXene electrodes require further modifications to facilitate reversible electrochemical reactions. Herein, through spontaneous intercalation of various metal ions into MXene multilayers, twelve metal ion intercalated MXene electrodes (Mⁿ⁺‐MXene) are fabricated and demonstrate improved electrochemical performance. Different nanopillar effects are observed between divalent Be²⁺ and trivalent Al³⁺ intercalants, which are systematically investigated by electrochemical impedance spectroscopy and molecular dynamics simulation. Among all Mⁿ⁺‐MXene electrodes, the Be²⁺‐MXene electrode largely facilitates the charge‐transfer process with minimal disturbance of electrolyte diffusion rates, showing improved specific capacitances and high rate performance in univalent (Li₂SO₄, Na₂SO₄, K₂SO₄) and multivalent electrolytes (BeSO₄, MgSO₄, ZnSO₄). Finally, flexible Be²⁺‐MXene MSCs with neural ZnSO₄ gel electrolytes are fabricated, demonstrating superior areal capacitances (77.2 mF cm^?2) and high energy density (3.86 μWh cm^?2 at 0.12 mW cm^?2) together with high user safety.     

Flexible MXene/Graphene Films for Ultrafast Supercapacitors with Outstanding Volumetric Capacitance

A strategy to prepare flexible and conductive MXene/graphene (reduced graphene oxide, rGO) supercapacitor electrodes by using electrostatic self‐assembly between positively charged rGO modified with poly(diallyldimethylammonium chloride) and negatively charged titanium carbide MXene nanosheets is presented. After electrostatic assembly, rGO nanosheets are inserted in‐between MXene layers. As a result, the self‐restacking of MXene nanosheets is effectively prevented, leading to a considerably increased interlayer spacing. Accelerated diffusion of electrolyte ions enables more electroactive sites to become accessible. The freestanding MXene/rGO‐5 wt% electrode displays a volumetric capacitance of 1040 F cm^?3 at a scan rate of 2 mV s^?1 , an impressive rate capability with 61% capacitance retention at 1 V s^?1 and long cycle life. Moreover, the fabricated binder‐free symmetric supercapacitor shows an ultrahigh volumetric energy density of 32.6 Wh L^?1, which is among the highest values reported for carbon and MXene based materials in aqueous electrolytes. This work provides fundamental insight into the effect of interlayer spacing on the electrochemical performance of 2D hybrid materials and sheds light on the design of next‐generation flexible, portable and highly integrated supercapacitors with high volumetric and rate performances.     

Strategy Toward Semiconducting Ti3C2Tx-MXene: Phenylsulfonic Acid Groups Modified Ti3C2Tx as Photosensitive Material for Flexible Visual Sensory-Neuromorphic System

The excellent electronic and electrochemical properties make 2D MXenes suitable candidates for sensors, batteries, and supercapacitors. However, the metallic-like behavior of MXenes hinders their potential for optoelectronic devices such as photodetectors. In this study, the band gap of metalloid Ti₃C₂T_x MXene is successfully opened to 1.53 eV with phenylsulfonic acid groups and realized a transistor and high-performance near-infrared photodetector array for a flexible vision sensory-neuromorphic system. The phenylsulfonic acid groups modified Ti₃C₂T_x MXene (S-Ti₃C₂T_x)-based flexible photodetector has a maximum responsivity of 8.50×10² A W⁻¹ and a detectivity of 3.69×10¹¹ Jones under 1064 nm laser irradiation. Moreover, the fabricated flexible vision sensory-neuromorphic system for image recognition realizes a high recognition rate >0.99, leading to great potential in the field of biological visual simulation and biomimetic eye. Besides conventional devices with Au as the conductive electrodes, all Ti₃C₂T_x MXene-based devices are also fabricated with S-Ti₃C₂T_x as the photosensitive material and unmodified Ti₃C₂T_x as the conductive electrodes, exhibiting comparable optoelectronic performances.     

Flexible MXene Framework as a Fast Electron/Potassium-Ion Dual-Function Conductor Boosting Stable Potassium Storage in Graphite Electrodes

Graphite anodes show great potential for potassium storage, however, their capacity fades quickly owing to substantial interlayer expansion/shrinkage (i.e., up to 60%) induced structural degradation. Here, Ti₃C₂T_x MXene nanosheets are used as a fast electron/potassium-ion dual-function conductor to construct the framework of all-integrated graphite nanoflake (GNF)/MXene (GNFM) electrodes. The continuous MXene framework constructs a 3D channel for fast electron/potassium-ion transfer and endows GNFM electrodes with a high structural stability. Owing to this unique MXene framework, GNFM electrodes exhibit much enhanced potassium storage performances than that of the conventional polymer-bonded electrodes even at high mass loadings. Moreover, GNFM electrodes also show impressive cyclability in non-flammable electrolytes and are further used as anodes to assemble novel non-flammable potassium-ion capacitors that show an excellent cyclability and high energy/power densities (113.1 Wh kg^–1 and 12.2 kW kg^–1). New insights into phase transition mechanism in GNFM electrodes are verified by operando XRD. Density functional theory calculations demonstrate that MXene can promote electron transfer and potassium diffusion in the heterointerface between GNF and MXene. Therefore, the results demonstrate that all-integrated GNFM electrodes designed with MXene as multifunctional frameworks provide a new paradigm for producing efficient potassium storage anodes.     

Large-Area Freestanding Bi2S3 Nanofibrous Membranes for Fast Photoresponse Flexible IR Imaging Photodetector

Films with excellent flexibility and mechanical stability are important for flexible and wearable devices. However, most films reported are prepared on substrates, and the synthesis of freestanding flexible films remains a challenge. Herein, a freestanding Bi₂S₃ nanofibrous membrane (NFM) is successfully prepared via a one-step hydrothermal method, which is self-assembled from ultralong Bi₂S₃ nanowires (NWs) over a length of millimeter-scale crisscrossing each other. Significantly, the Bi₂S₃ NFM can be bent or clipped into an arbitrarily desired form. Based on the freestanding Bi₂S₃ NFM, an IR photodetector is fabricated, depicting a robust responsivity of 2.23 (2.06) µA W⁻¹ under 850 (940) nm illumination. The Bi₂S₃ NFM photodetector exhibits a relatively fast response time (47.1 ms), which is attributed to high-speed carrier transport efficiency in the NWs network. Under the bending states, the device still exhibits excellent detection performance, maintaining more than 86% of the initial photocurrent even after 1000 bending-flattening times. The robust photoresponse of the Bi₂S₃ NFM photodetector after 2 months of storage in air and after 1 week in the bending state illustrates its excellent air stability and flexible detection ability. Besides, the photodetector can clearly identify the target image, indicating widespread potential applications in flexible and wearable fields.     

3D Porous Oxidation-Resistant MXene/Graphene Architectures Induced by In Situ Zinc Template toward High-Performance Supercapacitors

2D MXene materials have attracted intensive attention in energy storage application. However, MXene usually undergoes serious face-to-face restacking and inferior stability, significantly preventing its further commercial application. Herein, to suppress the oxidation and self-restacking of MXene, an efficient and fast self-assembly route to prepare a 3D porous oxidation-resistant MXene/graphene (PMG) composite with the assistance of an in situ sacrificial metallic zinc template is demonstrated. The self-assembled 3D porous architecture can effectively prevent the oxidation of MXene layers with no evident variation in electrical conductivity in air at room temperature after two months, guaranteeing outstanding electrical conductivity and abundant electrochemical active sites accessible to electrolyte ions. Consequently, the PMG-5 electrode possesses a striking specific capacitance of 393 F g⁻¹, superb rate performance (32.7% at 10 V s⁻¹), and outstanding cycling stability. Furthermore, the as-assembled asymmetric supercapacitor possesses a pronounced energy density of 50.8 Wh kg⁻¹ and remarkable cycling stability with a 4.3% deterioration of specific capacitance after 10 000 cycles. This work paves a new avenue to solve the two long-standing significant challenges of MXene in the future.     

Highly Stable Ag–Au Core–Shell Nanowire Network for ITO-Free Flexible Organic Electrochromic Device

Solid and flexible electrochromic (EC) devices require a delicate design of every component to meet the stringent requirements for transparency, flexibility, and deformation stability. However, the electrode technology in flexible EC devices stagnates, wherein brittle indium tin oxide (ITO) is the primary material. Meanwhile, the inflexibility of metal oxide usually used in an active layer and the leakage issue of liquid electrolyte further negatively affect EC device performance and lifetime. Herein, a novel and fully ITO-free flexible organic EC device is developed by using Ag–Au core–shell nanowire (Ag–Au NW) networks, EC polymer and LiBF₄/propylene carbonate/poly(methyl methacrylate) as electrodes, active layer, and solid electrolyte, respectively. The Ag–Au NW electrode integrated with a conjugated EC polymer together display excellent stability in harsh environments due to the tight encapsulation by the Au shell, and high area capacitance of 3.0 mF cm⁻² and specific capacitance of 23.2 F g⁻¹ at current density of 0.5 mA cm⁻². The device shows high EC performance with reversible transmittance modulation in the visible region (40.2% at 550 nm) and near-infrared region ( − 68.2% at 1600 nm). Moreover, the device presents excellent flexibility ( > 1000 bending cycles at the bending radius of 5 mm) and fast switching time (5.9 s).     

MXene‐Enabled Electrochemical Microfluidic Biosensor: Applications toward Multicomponent Continuous Monitoring in Whole Blood

Continuous and real‐time sensoring has received much attention in biomarker monitoring, toxicity assessment, and therapeutic agent tracking. However, its on‐site application is seriously limited by several stubborn defects including liability to fouling, signal drifting, short service life, poor repeatability, etc. Additionally, most current methods require extra sample pretreatment, delaying timely acquisition of testing results. To address these issues, MXene‐Ti₃C₂T_x based screen‐printed electrode incorporated with a dialysis microfluidic chip is constructed for a direct and continuous multicomponent analysis of whole blood. Dual‐function of MXene is developed and allows for simultaneous quantification of different target compounds through one device. Importantly, ratiometric sensing tactic is easily implemented in the system, which greatly alleviates signal drifting. As a proof of concept, this novel sensor is applied in hemodialysis, and continuous assay of urea, uric acid, and creatinine levels in human blood is realized. This work paves a new path for 2D MXene in biomedical and sensing applications.     

3D Macroscopic Architectures from Self‐Assembled MXene Hydrogels

Assembly of 2D MXene sheets into a 3D macroscopic architecture is highly desirable to overcome the severe restacking problem of 2D MXene sheets and develop MXene‐based functional materials. However, unlike graphene, 3D MXene macroassembly directly from the individual 2D sheets is hard to achieve for the intrinsic property of MXene. Here a new gelation method is reported to prepare a 3D structured hydrogel from 2D MXene sheets that is assisted by graphene oxide and a suitable reductant. As a supercapacitor electrode, the hydrogel delivers a superb capacitance up to 370 F g^?1 at 5 A g^?1, and more promisingly, demonstrates an exceptionally high rate performance with the capacitance of 165 F g^?1 even at 1000 A g^?1. Moreover, using controllable drying processes, MXene hydrogels are transformed into different monoliths with structures ranging from a loosely organized porous aerogel to a dense solid. As a result, a 3D porous MXene aerogel shows excellent adsorption capacity to simultaneously remove various classes of organic liquids and heavy metal ions while the dense solid has excellent mechanical performance with a high Young's modulus and hardness.