2D Carbide MXene under postetch low-temperature annealing for high–performance supercapacitor electrode

MXene, as an emerging class of conductive two-dimensional materials, have extraordinary applications in the field of electrochemical energy storage . However, the intrisic capacity of MXene still need to be improved due to the large gap to their theoretical capacity. Here, we provide a facile and new strategy to enhance their electrochemical performance—postetch low-temperature annealing (below 400 °C) under Ar atmosphere. Due to the formation of more C-Ti-O active sites and larger interlayer voids, the Ti 3 C 2 T x freestanding film annealed under 200 °C exhibits a high capacitance of 429 F/g and energy density of 29.2 Wh/Kg in 1 M H 2 SO 4 electrolyte, it could withstand 5000 cycles with 89% of the capacitance retention. By comparison, the Ti 3 C 2 T x annealed at higher temperature (400 °C), presented a high resistance and poor electrochemical property because of partial oxidation and breaking of Ti-C bond on the surface of MXene nanosheets , despite the larger interlayer voids and low –F contents, . This work is not only probing the importance to maintain the original structure of MXene but also proposing a new strategy to realizing a high capacitance of pure MXene electrode.