Supercritical etching method for the large-scale manufacturing of MXenes

MXenes as an emerging 2D materials have attracted significant attention in the fields of energy storage, sensing, etc. However, superlong time-consuming (several days) and low-production (⁓ 1 g) of dangerously F-contained acid etching method intrinsically make it inapplicable for large-scale manufacture of MXenes. Herein, we propose a supercritical etching method for the mass preparation of various MXenes assisted by supercritical carbon dioxide . The enhanced thermal power of supercritical carbon dioxide molecules helps significantly accelerate the etching rate of the MAX phase and increase the layer spacing of MXenes. As a result, five typical MAX materials (Ti 3 AlC 2 , Nb 2 AlC, Ti 2 AlC, Mo 2 Ga 2 C, and Ti 3 AlCN) can be exfoliated into the corresponding MXenes (Ti 3 C 2 T x , Nb 2 CT x , Ti 2 CT x , Mo 2 CT x , and Ti 3 CNT x ) with the yield of ∼ 1 Kg within 2–5 h. We further developed a Ti 3 C 2 T x -based Na-ion battery with a remarkable capacity of 100 mAh g −1 at 100 mA g −1 (70 mAh g −1 at 1000 mA g −1 ) and excellent coulombic efficiency of nearly 100%. The proposed supercritical etching strategy provides a platform for the commercial production of MXenes.