Antioxidants Unlock Shelf-Stable Ti3C2T (MXene) Nanosheet Dispersions

Although MXene nanosheets have attracted significant scientific and industrial attention, these materials are highly susceptible to oxidation, which leads to their chemical degradation and loss of functional properties in a matter of days. Here 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 with untreated ones after 21 days. This resistance to oxidation also persists in the dried state. We propose that the sodium L-ascorbate protects the edges of the nanosheets, restricting water molecules from otherwise reactive sites; this is supported by molecular dynamics simulations that show association of the ascorbate anion with the nanosheet edge.