Abstract:
Transition-metal carbides (MXenes) are an
emerging class of two-dimensional materials with promising
electrochemical energy storage performance. Herein, for the
first time, by direct chemical synthesis, nanocrystalline ε-MnO2
whiskers were formed on MXene nanosheet surfaces (ε-
MnO2/Ti2CTx and ε-MnO2/Ti3C2Tx) to make nanocomposite
electrodes for aqueous pseudocapacitors. The ε-MnO2 nanowhiskers
increase the surface area of the composite electrode
and enhance the specific capacitance by nearly 3 orders of
magnitude compared to that of pure MXene-based symmetric
supercapacitors. Combined with enhanced pseudocapacitance,
the fabricated ε-MnO2/MXene supercapacitors exhibited
excellent cycling stability with ∼88% of the initial specific capacitance retained after 10000 cycles which is much higher than
pure ε-MnO2-based supercapacitors (∼74%). The proposed electrode structure capitalizes on the high specific capacitance of
MnO2 and the ability of MXenes to improve conductivity and cycling stability
