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The authors report long-lived pump-induced conductivity suppression in metallic Ti₃C₂ MXenes using ultrafast terahertz and reflectance spectroscopy. The effect is attributed to strong photothermal heating and slow heat dissipation.

Fabrication of fully stretchable organic light-emitting diodes incorporating an intrinsically stretchable exciplex-assisted phosphorescent layer along with MXene-contact stretchable electrodes is described, demonstrating high efficiency and mechanical compliance for applications in next-generation wearable and deformable displays.

Effects from electrolytes on supercapacitor electrodes, especially pseudocapacitive materials, are important but often overlooked. Gogotsi and colleagues demonstrate strong influences from electrolyte solvents on charge-storage processes in a titanium carbide and identify a best-performing electrode/electrolyte couple for supercapacitors.

Two-dimensional materials show great potential for membrane technologies, but their disordered channels hinder their molecular sieving performance. Here, Wang, Gogotsi and colleagues design a MXene membrane with ordered nanochannels that exhibits an excellent H₂/CO₂ gas separation performance.

Modern communication applications may demand devices with tunable performances and simple fabrications. Here, we show strain dependent, adjustable RF/microwave performance by applying patterns of conductive Ti3C2Tx MXene coatings on low-cost acetate substrates in a straightforward coating process.

Authors show that water trapped between 2D MXene sheets forms amorphous ice clusters at low temperatures, which cause a hysteresis of electrical conductivity. This structural rearrangement of water is affected by the presence of solvated cations, allowing reversible switching of the electronic properties of MXene films.

Heterostructures with alternating layers of different 2D materials are finding increasing attention in energy applications. Pomerantseva and Gogotsi survey the opportunities and challenges of both developing the heterostructures and their implementation in energy storage devices.

The unique properties of 2D materials, such as graphene or transition metal dichalcogenides, have been attracting much attention in the past decade. Now, metallically conductive and even superconducting transition metal carbides are entering the game.

Salt-assisted assembly has been developed to achieve large-scale coating of MXene on polymer substrates. The process includes a library of salts and polymer substrates, opening new applications such as thermal management in extreme conditions.

Cables and wires are used to conduct electricity, but can they also store energy? The answer is a resounding 'yes', if they are encased by a supercapacitor device — a finding that might open up many applications.

It can be challenging for conventional electrochemical measurements to distinguish different types of charge storage mechanisms in electrochemical systems. Here the authors develop an in situ ultraviolet–visible spectroscopy approach as a powerful and affordable tool for this purpose.

Two-dimensional atomic crystals are known to be effective electrode materials for energy storage applications. Here, the authors report the preparation of various two-dimensional metal oxides, including those which do not have a layered parent structure, via a salt templating strategy.

Pseudocapacitors based on redox-active materials have relatively high energy density but suffer from low power capability. Here the authors report that two-dimensional transition metal carbides exhibit high gravimetric, volumetric and areal capacitance values at high charge/discharge rates.

Intercalation materials are of interest for batteries because of their capability of accommodating ions in their layered structures. Mashtalir et al. develop a new battery electrode material using two-dimensional intercalated carbides, which exhibit high lithium-ion conductivity and capacity.

2D MXene hydrogels are promising for diverse applications. Here, the authors report a universal 4D printing technology to manufacture MXene hydrogels with customizable geometry, high conductivity, and efficient pseudocapacitive energy storage ability.

Modulating the interaction of a thin film with microwaves is realized using the electrochemical behaviours of various MXenes.

Secondary-ion mass spectrometry shows the presence of oxygen in the carbon sublattice of MXene, demonstrating the existence of oxycarbide MXenes.

Although the superior electrochemical performance of supercapacitors capable of rapidly storing electrical energy is due to reversible ion adsorption in porous carbon electrodes, the molecular origin of this phenomenon is still poorly understood. A quantitative picture of the structure of an ionic liquid adsorbed inside realistically modelled microporous carbon electrodes is now proposed.

Micrometre-thick supercapacitors made from onion-like carbon nanoparticles exhibit orders of magnitude higher capacitance and energy density compared with electrolytic capacitors, and much higher charging/discharging rates than conventional supercapacitors.

By using a battery of experimental and theoretical methods, it is shown that ion intercalation into the electrode material birnessite is mediated by structural water.

Single-atom catalysts are very attractive due to their ability to maintain high activities at the lowest possible precious metal loading. Here, a double transition metal MXene that effectively anchors single Pt atoms is reported, and exhibits superior performance and stability towards the hydrogen evolution reaction.

Improving the accessibility of ions in the electrodes of electrochemical energy storage devices is vital for charge storage and rate performance. Here, the authors report a new type of MXene-carbon nanotube composite electrode that maximizes ion accessibility, resulting in high rate performance at low temperatures.

Developing thick electrodes could enable high-energy-density Li-ion batteries, however, above a critical thickness, the mass transport issues become dominating. Here the authors show that MXene can serve as a conductive binder leading to thick silicon anodes (up to 450 µm) with high areal capacity.

Printing functional inks is attractive for applications in electrochemical energy storage and smart electronics, among others. Here the authors report highly concentrated, additive-free, aqueous and organic MXene-based inks that can be used for high-resolution extrusion and inkjet printing.

Here, authors demonstrate the electrohydrodynamic printing of alkylated 3,4-dihydroxy-L-phenylalanine functionalized MXene (AD-MXene) ink. The AD-MXene outperforms vacuum-deposited Au and Al electrodes, providing thin film transistors with good environmental stability due to its hydrophobicity.

Permeation experiments and simulations show that the ion diffusion rate in confinement can be reversibly modulated and significantly enhanced with a potential of less than 0.5 V.

Lithium metal is an ideal anode material for rechargeable batteries but suffer from the growth of lithium dendrites and low Coulombic efficiency. Here the authors show that nanodiamonds serve as an electrolyte additive to co-deposit with lithium metal and suppress the formation of dendrites.

An endoscope formed by attaching carbon nanotubes to the tips of glass micropipettes can be used to probe intracellular processes, and transport fluids and nanoparticles to and from precise locations.

Intercalation of protons in 2D materials plays a major role for several applications in energy storage and conversion. Here, the authors show that protons intercalated in Ti₃C₂T_x MXene interlayer during electrochemical cycling have a different hydration structure than protons in bulk water.

The poor dispersibility of 2D hexagonal boron nitride in water currently limits its exfoliation and applications. Here, the authors present a one-step mechano-chemical process to achieve unprecedented colloidal concentrations, which permits fabrication of ultralight aerogels and freestanding membranes.

Separation of isotopes of heavier gases than hydrogen or helium is essential for biomedical applications, but current methods are very energy and time consuming. Here the authors report cryogenic separation of oxygen and methane isotopes through adsorption in nanoporous materials, based on a collective nuclear quantum effect.

Understanding bottom-up growth mechanisms of 2D transition metal carbides (MXenes) may enable new synthetic routes to tailor functional properties. Here, the authors use in situ electron microscopy, density functional theory and molecular dynamics simulations to reveal the homoepitaxial growth mechanisms of a single TiC adlayer from a Ti₃C₂ monolayer substrate.

Two-dimensional transition metal carbides and nitrides (MXenes) have emerged as highly conductive and stable materials, of promise for electronic applications. Here, the authors use in situ electric biasing and transmission electron microscopy to investigate the effect of surface termination and intercalation on electronic properties.

The structure of ionic liquids under confinement is not well understood and hinders their widespread use for applications. Convincing evidence of partial breaking of Coulombic ordering of ions confined in subnanometre carbon pores is now provided.

Electrode films prepared from a liquid-crystal phase of vertically aligned two-dimensional titanium carbide show electrochemical energy storage that is nearly independent of film thickness.

Two-dimensional titanium carbide has been produced by etching out aluminium in a lithium fluoride and hydrochloric acid mixture; it is hydrophilic and mouldable like clay and has excellent volumetric capacitance and cyclability, properties that are desirable for portable electronics.

MXenes are 2D materials with a rich chemistry and applications in energy storage, electronics and biomedicine. This Review discusses various MXene syntheses—from layered precursors to single-layer 2D flakes—including principles behind these methods and synthesis–structure–property relationships.

Electrochemical charge storage in a confined space is often interpreted as either electrostatic adsorption or Faradaic intercalation. Here the authors propose that the storage mechanism is a continuous transition between the two phenomena depending on the extent of ion solvation and ion–host interaction.

MXenes are two-dimensional materials with diverse optoelectronic, biological, mechanical and chemical properties. This protocol describes how to prepare single-layer flakes of Ti₃C₂T_x, the most important and widely used MXene, from a Ti₃AlC₂ MAX phase precursor.

With the continued miniaturization of electronics, there are increasing efforts to engineer small, powerful energy storage devices. Here the authors review the cutting edge of this rapidly developing field, highlighting the most promising materials and architectures for our future energy storage requirements.

Dramatic innovations in surface and bulk chemistry enable MXenes to flourish in electrochemical applications. This Review analyses the recorded footprints of MXene components for energy storage, with particular attention paid to a coherent understanding of the fundamental relationship between MXene components and their qualified roles from a nuanced chemical perspective.

Electrochemical capacitors can store electrical energy harvested from intermittent sources and deliver energy quickly, but increased energy density is required for flexible and wearable electronics and larger equipment. Progress in materials and devices and key perspectives in this field are outlined.

The development of efficient, high-energy and high-power electrochemical energy-storage devices requires a systems-level holistic approach, rather than focusing on the electrode or electrolyte separately. In this Review, we discuss the interfacial reactions and ion transport in ionic-liquid-based Li-ion batteries and supercapacitors, and summarize their impact on device performance.