  There are emerging applications for photothermal conversion utilizing MXene,
but the mechanism under these applications related interfacial energy migration
from MXene to the attached surface layer is still unknown. In this paper, with
comprehensive ultrafast studies, we reported the energy migration pathway from
MXene (Ti3C2Tx) to local environment under plasmonic excitation. Our data found
that in water, energy dissipation is divided into fast hydrogen bond mediated
channel and slow lattice motion mediated channel.The experimental results
suggest that in water, nearly 80% energy in MXene that gained from the
photoexcitation quickly dissipates into surrounding water molecules within 7 ps
as a hydrogen bond mediated fast channel, and the remaining energy vanishes
with time constant ~100 ps as a lattice motion mediated slow channel. The fast
energy migration would result in the prominent interfacial energy conductance
150-300 MW *m{-2}* K{-1} for MXene-water interface. Tuning the solvent into
ethanol could both narrow the energy dissipation to 35% through the fast
channel and slow down the thermal channel (400 ps). To gain the molecular
insight, molecular dynamic results presented different solvents had
significantly different H bond forming ability on MXene surface. Our results
suggested that interfacial interaction is crucial for effective hydrogen bonds
on MXene surface to channel the excitation dissipation, providing important
insights into the photothermal applications with MXene.
