X. Zhao, T. Habib, E. Prehn, W. Sun, S.A. Shah, Y. Chen, Z. Tan, J. Lutkenhaus, M. Radovic, M.J. Green
Texas A&M University,
Keywords: MXene, MAX, nanosheet, oxidation, scalable
Summary:Ti3C2Tx belongs to the fascinating family of MXenes, 2D materials with an attractive combination of functional properties suitable for applications such as batteries, supercapacitors, and strain sensors. However, fabrication of devices and functional coatings based on Ti3C2Tx remains challenging as they are prone to chemical degradation by oxidation into TiO2. In this paper, we examine oxidation of Ti3C2Tx in various media (air, liquid, and solid) via conductivity measurements to assess the shelf life of Ti3C2Tx MXenes. The oxidation of Ti3C2Tx was observed in all media used in this study, but it is fastest in liquid media and slowest in solid media (including polymer matrices), and is accelerated by exposure to UV light. More importantly, we demonstrate an effective method to prevent the oxidation of colloidal Ti3C2Tx MXene nanosheets by using sodium L-ascorbate as an antioxidant. The success of the method is evident in the stable morphology, structure, and colloidal stability of Ti3C2Tx. Even in the presence of water and oxygen, the electrical conductivity of Ti3C2Tx nanosheets treated with sodium L-ascorbate was orders of magnitude higher as compared to untreated ones after 21 days. This resistance to oxidation persists in the dried state as well. These findings have the potential to be generalized to protect other types of MXenes as well and solve the most pressing challenge in the field of MXene engineering.