MXene

MXene is a family of two-dimensional transition metal carbides, nitrides, and carbonitrides. They are produced by selectively etching the A-layer from MAX phases, a class of layered materials discovered in 2011 by researchers Naguib and Gogotsi. The name MXene reflects their composition: “M” denotes a transition metal, “X” stands for carbon and/or nitrogen, and the suffix “ene” signals their two-dimensional nature.

MXenes have the general formula Mn+1Xn, where M is an early transition metal (such as titanium, niobium, or vanadium), X is carbon and/or nitrogen, and A is an A-group element (typically aluminum or silicon) that is removed during synthesis. After etching, the resulting Mn+1Xn layers are capped by surface terminations T, commonly oxygen, hydroxyl, and/or fluorine, giving formulas like Ti3C2Tx. The materials are typically produced as few-layer stacks with negative surface charges and can be processed into powders, films, or inks.

Most common synthesis uses HF or fluoride salts to remove A layers from MAX phases (for example Ti3AlC2 to Ti3C2Tx). Delamination into few-layer MXene is achieved using intercalants such as Li+, followed by exfoliation in water or organic solvents. The materials form stable dispersions and can be assembled into electrodes, films, or composites.

MXenes exhibit high electrical conductivity, hydrophilicity, and mechanical strength, with a large surface area and tunable surface chemistry via terminations and intercalants. They are investigated for energy storage (supercapacitors, Li- and Na-ion batteries), catalysis, electromagnetic interference shielding, sensors, and water purification, as well as for composites and coatings.

Challenges include oxidation in air, restacking that reduces accessible surface area, batch variability, and safety concerns linked to hydrofluoric acid. Research explores HF-free syntheses and scalable production methods.