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 (Ti3AlC2, Nb2AlC, Ti2AlC, Mo2Ga2C, and Ti3AlCN) can be exfoliated into the corresponding MXenes (Ti3C2Tx, Nb2CTx, Ti2CTx, Mo2CTx, and Ti3CNTx) with the yield of ∼ 1 Kg within 2–5 h. We further developed a Ti3C2Tx-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.