(363b) Electrochemical Etching and Oxidation Stability of Mxene Nanosheets

MXenes are a new group of 2D nanosheets that hold promise for a range of functional material applications. They are derived from MAX phases, which have the chemical composition M_n+1AX_n, where n = 1, 2 or 3 (M₂AX, M₃X₂, or M₄AX₃), “M” is an early transition metal, “A” is an A group (mostly groups 13 and 14) element, and “X” is C and/or N. Highly hazardous HF or LiF/HCl solution is widely used to remove A layer from parent MAX phase to get MXenes with a combination of -F, -OH, -O, or/and -Cl terminal groups. Here we successfully demonstrate the electrochemical etching of Al from porous Ti₂AlC in dilute HCl solution, with no use of toxic fluoride solutions. This approach is a less hazardous method to process and handle MXenes compared to prior works. We also observed that electrochemical etching can result in subsequent over-etching to carbide-derived carbon. In addition, we studied MXene oxidation in various media. We observed 1) faster oxidation in liquid media than in solid media, 2) continuous oxidation in pure MXene films and MXene/polymer composites, and 3) accelerated MXene film oxidation under UV irradiation.