Beschreibung:
Although MXene shows tremendous application potential, it has always been subjected to its ambient instability and disadvantages of fluorine-containing. The preparation of fluorine-free MXene with excellent ambient stability remains a persistent challenge. Here, we systematically study the oxidative degradation process of Ti3C2Tx-MXene and find that factors affecting its environmental instability may be related to the incomplete or non-uniform coverage of surface groups, which caused by competitive surface adsorption of fluorine-containing by-products. Based on our understanding of the oxidative degradation process, we selected tetramethylammonium hydroxide as a separate etching agent and successfully prepared fluorine-free Ti3C2Tx after a long period of etching (7 days). Interestingly, the resulting fluorine-free Ti3C2Tx is environmentally stable and can be continuously stored without oxidation even if dispersed in water, while conventional Ti3C2Tx water dispersions can only be stored for a few days. In addition, in the seawater desalination application, we found that the conventional Ti3C2Tx would cause harmful elements (F and Ti) to be mixed into desalinated water due to their instability. In contrast, the prepared fluorine-free and environmentally stable Ti3C2Tx not only avoided the above drawback, but also exhibited a more excellent seawater desalination ability, with Na+ permeability decreasing by a maximum of 62.2% and a maximum increase in water flux by 300%. This work advances the understanding of the environmental instability of Ti3C2Tx MXene and provides a facile approach to obtain the highly anticipated fluorine-free and environmentally stable Ti3C2Tx