Universal salt-assisted assembly of MXene from solution on polymers

Abstract Two-dimensional carbides and nitrides known as MXenes are promising water-processable coating materials with excellent electrical conductivity, and thermal and optical properties¹. However, deposition of hydrophilic MXene nanosheets on inert and/or hydrophobic surfaces of polymer or textiles requires plasma treatment or chemical surface modification²,³. Herein, we demonstrate a universal salt-assisted assembly from a solution that produces ultra-thin and uniform MXene coatings with outstanding mechanical stability and washability on diverse polymers, including high-performance polymers for applications under extreme temperature conditions. The salt added to the Ti₃C₂Tx aqueous colloid neutralizes MXene’s surface charge and deposits MXene onto the polymer surface. Molecular dynamics simulations suggest a decreasing interlayer spacing due to the expulsion of water molecules and anions, while cations are trapped between the MXene layers. A library of salts has been used to tailor the assembly kinetics and coating morphology. A 170 nm MXene coating for thermal management enables a ~200 °C radiation temperature drop on a 300 °C PEEK substrate, greatly decreasing energy loss. Joule heating of Kevlar fabric with ~870 nm MXene coating using a 4 V battery sustains comfortable for human conditions at -80 °C outside temperature and can be used in extreme environments such as outer space, polar regions, and high altitudes.