Thermal transport in Ti3C2 MXene enhanced by hydrogen functionalization-induced symmetry reconstruction

Abstract

MXenes, with their diverse functional groups, tunable surface structures, and exceptional chemical versatility, offer significant potential for modulating thermal transport properties, enabling their application in electronic devices and energy storage. In this work, we systematically investigate how hydrogen functionalization and the resulting symmetry reconstruction affect the in-plane thermal transport characteristics of the representative MXene Ti3C2, using a Boltzmann transport framework for both lattice and electronic contributions. Our results show that particle-like phonons predominantly dominate the lattice thermal conductivity, whereas the wave-like phonon tunneling contribution is negligible due to long phonon lifetimes. Hydrogen-induced symmetry reconstruction weakens both three- and four-phonon scattering processes and enhances phonon group velocities, resulting in a pronounced increase in thermal conductivity. Consequently, the lattice thermal conductivity rises by more than 20% after functionalization. Comparing different hydrogen terminations, the lattice thermal conductivity of asymmetrically functionalized Ti3C2H2 is slightly lower than that of its symmetrically functionalized counterpart. The reduction primarily stems from inversion-symmetry breaking in the asymmetric structure, which enlarges the phonon scattering cross section. Moreover, hydrogen functionalization-induced symmetry reconstruction markedly suppresses electronic thermal transport and fundamentally reshapes thermal anisotropy, particularly near the p-type Van Hove singularity. Notably, asymmetric Ti3C2H2 achieves a peak thermoelectric figure of merit of 1.13 at the p-type Van Hove singularity at 300 K—over 7.5 times higher than that of pristine Ti3C2. These findings highlight symmetry reconstruction via surface hydrogen functionalization as a powerful strategy for enhancing thermal transport performance in MXenes.