(133f) Enhancing the Oxidative Stability of Mxenes

The oxidation of 2D MXenes jeopardizes their shelf life, both in colloidal dispersions and in functional energy-storage devices. Our group has developed several approaches to prevent MXene oxidation, including low-temperature storage, antioxidants, and thermal annealing. Antioxidants in particular have been shown to effectively mitigate oxidation of MXenes (such as sodium L-ascorbate, ascorbic acid, and polyanions), but the nature of interaction between these antioxidants and MXene remains unknown, which impedes the future selection and design of improved protection. This work systematically examines the interactions between three classes of antioxidant candidates, α-hydroxy acids, polycarboxylic acids, and phenols with Ti_n+1C_nT_x MXenes, specifically Ti₃C₂T_x and Ti₂CT_x. Interestingly, while some antioxidants provided no protection for the MXenes, and some antioxidants even accelerated their degradation, three antioxidants (e.g., citric acid, tartaric acid, and oxalic acid) protected the MXene nanosheets exceptionally well, showing minimum MXene degradation storage. Analysis of the antioxidants’ molecular structure and efficacy suggests that chelation interactions with the transition metal atoms of the nanosheets play a key role in effective protection of MXenes from oxidation.