2-D
Ti3C2TX MXene nanosheets are
obtained by etching Ti3SiC2 MAX phase that is
synthesized by heating the elemental Ti, Si, and C mixture at high
temperature. The electron emission behavior of both Ti3C2TX MXene and Ti3SiC2 MAX phase is studied. MXene exhibits excellent field emission characteristics
with a turn-on field of 4.7 V μm–1, and that
for the Ti3SiC2 MAX phase is 6.5 V μm–1. The turn-on electric field corresponding to an emission
current density of 10 μA cm–2 is 5.0 V μm–1 for Ti3C2TX MXene
and 7.5 V μm–1 for the Ti3SiC2 MAX phase. The calculated enhancement factor of MXene nanosheets
is ∼4280, which is one of the highest reported enhancement
factors to date. In order to get theoretical insight into the field
emission properties for Ti3C2 and OH-terminated
Ti3C2 MXene in comparison to the Ti3SiC2 MAX phase, we have presented the structure and electronic
properties from state of the art density functional theory (DFT) simulations.
The interaction of – OH with Ti3C2 involves
charge transfer from the “Ti” 3d orbital to −OH.
The computed work function follows the trend Ti3SiC2 > Ti3C2 > Ti3C2/OH, which supports the maximum field emission in −OH-terminated
Ti3C2 MXene and the minimum field emission in
the Ti3SiC2 MAX phase.