Oxidation stability of Ti3C2Tx MXene nanosheets in solvents and composite films

Ti3C2Tx belongs to the family of MXenes, 2D materials with an attractive combination of functional properties suitable for applications such as batteries, supercapacitors, and strain sensors. However, the fabrication of devices and functional coatings based on Ti3C2Tx remains challenging as they are prone to chemical degradation by their oxidation to TiO2. In this paper, we examine the oxidation of Ti3C2Tx in air, liquid, and solid media via conductivity measurements to assess the shelf life of Ti3C2Tx MXenes. The oxidation of Ti3C2Tx was observed in all the media used in this study, but it is fastest in liquid media and slowest in solid media (including polymer matrices). We also show that the conventional indicators of MXene oxidation, such as changes in color and colloidal stability, are not always reliable. Finally, we demonstrate the acceleration of oxidation under exposure to UV light.MXenes: oxidation pathways of Ti 3 C 2 T x nanosheetsThe storage and dispersion of MXene films in media influence their oxidation behavior. A team led by Miladin Radovic and Micah Green at Texas A&M University investigated the oxidation dynamics of Ti3C2Tx in air, liquids (water, acetone, and acetonitrile), and solids (ice and polymer), with the purpose of gaining insight into the interplay between degradation and storage in media. A decrease in conductivity, indicative of the degree of oxidation, was consistently observed with longer exposure times; the oxidation was the slowest in solid media and the fastest in liquid media. In aqueous dispersions, Ti3C2Tx oxidized in 2 weeks, along with a sharp decrease in electrical conductivity; however, the dispersion retained its dark color and colloidal stability. Ti3C2Tx could be well preserved in ice, whereas its polymers were not effective barriers to decrease oxidation.