formulations that can maximize surface area accessibility and ion transport within electrodes while minimizing space and environmental impact. Consequently, Additive Manufacturing (AM) technologies, which are capable of printing 3D objects and complex structures, offer unique possibilities to bring novel electrode materials into highperformance EES devices. Among the AM technologies, continuous extrusion-based 3D printing (also called direct ink writing or robocasting) is a versatile and costeffective processing route where the formulation and properties of colloidal inks directly control the printability and architecture of printed parts. It further offers the ability to integrate functional materials of different surface chemistry and dimensionality into EES devices [1] such as Li-ion batteries, [2][3][4] micro-supercapacitors (MSCs), [5,6] and wearable electronics. [7,8] Recently, 2D transition metal carbides, called MXenes (M n+1 X n T x , with M representing an early transition metal, X representing C and/or N and, and T x representing the terminal functional groups), [9,10] have shown huge potential as electrode materials for supercapacitors. [11,12] Their combination of metallic conductivity, high density (3.8 ± 0.3 g cm −3 ), and redox active, negatively charged surfaces can lead to superior charge storage and transfer capabilities when compared to other 2D materials. Their surface functional groups (O, OH, and F) further render them hydrophilic allowing them to be easily dispersed into aqueous suspensions and inks for processing electrodes using different approaches such as vacuum filtration, [10,13] spin coating, [14,15] screen printing, [16,17] stamping, [18] and spraying. [19][20][21] While these approaches show the potential of MXene for water-based processing of EES devices, limitations remain with respect to architectural control, scalability, or cost-effectiveness that could be addressed by employing 3D printing technologies. Although MXene aqueous inks have been recently employed in commercial pens for direct writing functional films, [22] the development of 3D printable MXene inks and their integration into customized 3D device architectures is still unexplored. In order to realize this challenge, these materials need to be integrated into inks with very specific rheological properties that allow smooth flow through narrow nozzles while still enabling the extruded filaments to retain their shape even after multiple layers are Additive manufacturing (AM) technologies appear as a paradigm for scalable manufacture of electrochemical energy storage (EES) devices, where complex 3D architectures are typically required but are hard to achieve using conventional techniques. The combination of these technologies and innovative material formulations that maximize surface area accessibility and ion transport within electrodes while minimizing space are of growing interest. Herein, aqueous inks composed of atomically thin (1-3 nm) 2D Ti 3 C 2 T x with large lateral size of about 8 µm possessing ideal vis...

Two-dimensional materials, such as graphene and molybdenum disulfide (MoS2), can greatly increase the performance of electrochemical energy storage devices because of the combination of high surface area and electrical conductivity. Here, we have investigated the performance of solution exfoliated MoS2 thin flexible membranes as supercapacitor electrodes in a symmetrical coin cell arrangement using an aqueous electrolyte (Na2SO4). By adding highly conductive graphene to form nanocomposite membranes, it was possible to increase the specific capacitance by reducing the resistivity of the electrode and altering the morphology of the membrane. With continued charge/discharge cycles the performance of the membranes was found to increase significantly (up to 800%), because of partial re-exfoliation of the layered material with continued ion intercalation, as well as increasing the specific capacitance through intercalation pseudocapacitance. These results demonstrate a simple and scalable application of layered 2D materials toward electrochemical energy storage.

Electrically conductive composites comprising polymers and graphene are extremely versatile and have a wide range of potential applications. The conductivity of these composites depends on the choice of polymer matrix, the type of graphene filler, the processing methodology, and any post-production treatments. In this review, we discuss the progress in graphene–polymer composites for electrical applications. Graphene filler types are reviewed, the progress in modelling these composites is outlined, the current optimal composites are presented, and the example of strain sensors is used to demonstrate their application.

Laminar membranes of two-dimensional materials are excellent candidates for applications in water filtration due to the formation of nanocapillaries between individual crystals that can exhibit a molecular and ionic sieving effect, while allowing high water flux. This approach has been exemplified previously with graphene oxide, however these membranes suffer from swelling when exposed to liquid water, leading to low salt rejection and reducing their applicability for desalination applications. Here, we demonstrate that by producing thin (∼5 μm) laminar membranes of exfoliated molybdenum disulfide (MoS) in a straightforward and scalable process, followed by a simple chemical functionalization step, we can efficiently reject ∼99% of the ions commonly found in seawater, while maintaining water fluxes significantly higher (∼5 times) than those reported for graphene oxide membranes. These functionalized MoS membranes exhibit excellent long-term stability with no swelling and consequent decrease in ion rejection, when immersed in water for periods exceeding 6 months. Similar stability is observed when exposed to organic solvents, indicating that they are ideal for a variety of technologically important filtration applications.