Preparation of Ti3C2 and Ti2C MXenes by fluoride salts etching and methane adsorptive properties

Here we reported the preparation of Ti 3 C 2 MXene and Ti 2 C MXene by etching Ti 3 AlC 2 and Ti 2 AlC with various fluoride salts in hydrochloric acid (HCl), including lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), and ammonium fluoride (NH 4 F). As-prepared Ti 2 C was further delaminated by urea, dimethylsulfoxide or ammonium hydroxide. Based on theoretical calculation and XPS results, the type of positive ions (Li + , Na + , K + , or NH 4 + ) in etchant solution affect the surface structure of prepared MXene, which, in turn, affects the methane adsorption properties of MXene. The highest methane adsorption capacity is 8.5   cm 3 /g for Ti 3 C 2 and 11.6   cm 3 /g for Ti 2 C. MXenes made from LiF and NH 4 F can absorb methane under high pressure and can keep methane under normal pressure, these MXenes may have important application on capturing methane or other hazardous gas molecules. MXenes made from NaF and KF can absorb methane under high pressure and release methane under low pressure. They can have important application in the adsorb storage of nature gas.