A comprehensive overview of recent progress in MXene-based polymer composites: Their fabrication processes, advanced applications, and prospects

Abstract

MXenes are a group of 2D transition metal carbonitrides, nitrides and carbides that have become widely recognized as useful materials since they were first discovered in 2011. MXenes, with their exceptional layered structures and splendid external chemistries, have excellent electrical, optical, and thermal properties, making them suitable for catalysis, biomedical uses, environmental remediation, energy storage, and EMI shielding. Over forty MXene compounds with surface terminations like hydroxyl, oxygen, or fluorine are hydrophilic and easily integrated into various applications. Advanced synthesis methods, including selective etching and etchant modifications, have broadened MXene surface chemistries for customized mechanical, thermal, and electrical applications. Integrating MXenes into polymer composites has demonstrated notable promise, enhancing the host polymers' electrical conductivity, thermal stability and mechanical strength. The MXene-polymer composites demonstrate remarkable prospective on behalf of advanced purposes, including flexible electronics, high-performance EMI shielding materials, and lightweight structural components. MXenes have the desirable characteristic of being able to create flexible and translucent films, as well as improve the properties of polymer matrices. This makes them very suitable for use in advanced technological applications. This review summarizes MXene research, methods, and insights, highlighting key discoveries and future directions. This also highlights the importance of ongoing research to fill in the gaps in current knowledge and improve the practical uses of MXenes.

Keywords: EMI shielding; MXenes; Nanofillers; Polymer composites; Protective coatings.

Graphical abstract

Fig. 1

minations, X is either N or C, and M is an early transition metal. The range of the n value is 1–4. One, two, or more transition metal atoms can occupy the M sites to form ordered structures or solid solutions. (a) MAX phase structures and the MXenes that correspond with them. (b) Typical MXene structures and mixtures. (c) The structural and molecular formula of MXenes, were found experimentally.

Fig. 2

Magnetic characteristics of MXene.

Fig. 3

The provided images are scanning electron microscope (SEM) images of MXenes and MAX powders that have been produced using etching processes under various conditions. Scanning electron microscope (SEM) images of (a) Ti₃AlC₂ (MAX) powder displaying a dense layered arrangement and (b) multilayered Ti₃C₂T_x powder produced using hydrofluoric acid (HF) synthesis at 30 %, 10 %, and 5 % weight percentages. An accordion-like morphology was only detected after etching in a solution containing 30 wt percent HF or higher concentrations of HF. The NH₄– Ti₃C₂T_x powder, synthesized using ammonium hydrogen fluoride and the MILD method (etched with LiF in HCl), exhibits minimal opening of MXene lamellas, comparable to what is reported in 5F Ti₃C₂T_x. The SEM photos show individual MXene flakes on a porous alumina substrate that were etched using a combination of 5 % HF and MILD methods [87].

Fig. 4

MXenes synthesis routes timeline in the last decade.

Fig. 5

(a) Three different MXene (non-terminated) structures—M₂X, M₃X₂, and M₄X₃—were first described. (b) Ti₂AlC, Ti₃AlC₂, and Ti₄AlC₃ SEM images following HF treatment (from right to left). (c) Schematic representation of the synthesis of MXenes from MAX phases [87].

Fig. 6

MXene synthesis by MS-E-etching from the MAX phase, then controlled surface terminations made possible by salt lakes' plentiful supplies of potassium and lithium. Notably, the process is more controllable due to using eutectic salts, including KCl and LiCl, with a low melting point [134].

Fig. 7

MXene-reinforced polymer composites are created by physically integrating MXene with polymer matrices. Ti3C2Tx/SAF/PP composites are synthesized through the melt-mixing technique. (a) Composite films of PVA/MXene are fabricated using the casting method. (b) PVA/MXene composite films are prepared using the casting process. (c) ANF/MXene films are produced via the filtration method.

Fig. 8

Composites made of polymers reinforced with MXene are created by altering its surface. (a) The N-MXene/S composites' preparation procedure. (b) HC-MXene/TiO₂ electrodes are created mechanically, using Ti₃C₂Tx as a multipurpose conducting agent. (c) The PLA composites' preparation procedure. (d) EP preparation and PEPA-IPTS and PEPA-IPTS@ Ti₃C₂Tx synthesis.

Fig. 9

Polymers are deposited directly onto MXene surfaces using in situ methods. (a) Diagram illustrating the arrangement of PPy on the surface of MXene. (b) The impact of the pyrrole content on the volumetric and gravimetric capacitance of PPy/Ti₃C₂T_z hybrid electrodes is studied at a CV scan rate of 5 mV s⁻¹. (c) A cross-sectional transmission electron microscopy (TEM) picture showing the arrangement of PPy chains between MXene layers. (d) The ability of a 13 μm thick PPy/Ti₃C₂T_z electrode to handle high rates of operation. (e) Diagram illustrating the procedure used to produce the Ti₃C₂T_z/PANI hybrid film. (f) Schematic illustration depicting the process of aniline polymerization on MXene surfaces. (g) Electrochemical voltage curves of the Ti₃C₂T_z/PANI hybrid electrode at various scan speeds. Comparison of the rate capabilities of Ti₃C₂T_z/PANI hybrid electrodes with varying mass loadings. M refers to electrodes made of pure Ti₃C₂T_z, whereas M/PANI refers to electrodes that are a mix of Ti₃C₂T_z and PANI [150].

Fig. 10

(a) Thermal conductivity (a) and Thermal conductivity enhancement factor (TCE) (b) of GO/MXene and GM film with different contents of MXen; Agari’s model fitting curve of the film (c) GO/MXene film, (d) GM film [171].

Fig. 11

Mechanical characteristics of nanocomposite films based on MXene. (A) Schematic diagram showing the nanocomposite films based on MXene and pure MXene film. (B) The MXene-PVA nanocomposite films' stress-strain curves. Diagrammatic representation of MXene-CNF hybrid dispersion (C). (D) MXene-CNF nanocomposite film stress-strain curves both before and after vacuum pressing.

Fig. 12

Schematics of silane functionalization of PIPD fibers and subsequent addition of Ti₃C₂(OH)₂.

Fig. 13

(a) Production illustration of MXene paper. (b) Modeling demonstration and (c) Digital photographs of the fire sensor. Fire sensor operation stages showing (d) Pure MXene paper and (e) Conductivity characteristics of PVP-modified MXenes.

Fig. 14

(a) MXene-based ECs. Source (b) Cyclic voltammetry (CV) of the Li-Nb2CTx-400 electrode (scanning rate: 0.5 mV s-1). (c) Galvanostatic discharge-charge (GDC) results of the initial cycle for different Nb2CTx electrodes at 0.05 A g-1. (d) Cycling performance in terms of specific capacity for samples annealed at 2.0 A g-1. (e) Production process of the MXene aerogel. (f) Capacity cycling performance of the aerogel.

Fig. 15

(a)The atomic structure of various MAX phases can be determined by considering the number of ‘M' layers and the matching 2D MXenes obtained by removing the ‘A' layer through etching. (b) Diagram showing the process of creating MXene sheets from compressed MAX phases. (c) An aqueous dispersion of Ti₃C₂T_x MXene exhibits the Tyndall effect and can be processed into various shapes using (d) vacuum-assisted filtering, (e) spray coating, and (f) blade coating. (g) The electrical conductivity of MXenes, particularly Ti₃C₂T_x, normally improves over time.

Fig. 16

Diagrammatic representation of PVP-modified 2D biodegradable Nb2C for in vivo photothermal tumor ablation in NIR-I and NIR-II bio-windows (A) and (B). TEM picture of Nb2C-PVP/PBS (C). Photographs (D–F) showing the tumor regions and 4T1-bearing mice 16 days following various treatments (control (D), Nb2C-PVP + NIR-I (E), and Nb2C-PVP + NIR-II (F)). (G) Tumor growth curves that rely on time (n = 5, mean ± SD) following various treatments. (H) Mice survival curves following different treatments.