Molten salt electrochemical synthesis of low-cost Vn+1AlCn (n=1,3) and their derived two-dimensional MXenes

Herein we report a molten salt electrochemical approach to synthesize two MAX phases, V 2 AlC and V 4 AlC 3 , using inexpensive V 2 O 3 , Al 2 O 3 , and graphite as raw materials. The oxides/carbon mixture is directly reduced into MAX phases under cathodic polarization at moderate temperatures (600–850 °C). The corresponding MXenes, V 2 CT x and V 4 C 3 T x , are successfully produced through the HF etching method. The optimized molar ratio of V 2 O 3 /Al 2 O 3 /C precursor for V 2 AlC synthesis is achieved, and the resulting V 2 CT x film possesses great stability in air at 30 °C for at least 10 days. Furthermore, the obtained V 2 CT x and V 4 C 3 T x exhibit excellent capacities of 468 mAh g −1 and 152 mAh g −1 after 100 cycles, respectively, at a current density of 100 mA/g, comparable to those made from conventional methods.