Thermoelectric performance of functionalized ${\mathrm{Sc}}_2\mathrm{C}$ MXenes

Functionalization of the MXene ${\mathrm{Sc}}_2\mathrm{C}$, which has the rare property to realize semiconducting states for various functionalizations including O, F, and OH, is studied with respect to the electronic and thermal behavior. The lowest lattice thermal conductivity is obtained for OH functionalization and an additional 30% decrease can be achieved by confining the phonon mean free path to 100 nm. Despite a relatively low Seebeck coefficient, ${\mathrm{Sc}}_2\mathrm{C}({\mathrm{OH})}_2$ is a candidate for intermediate-temperature thermoelectric applications due to compensation by a high electrical conductivity and very low lattice thermal conductivity.

Figure 1

Atomic structure: Side and top views of monolayer ${\mathrm{Sc}}_2\mathrm{C}$ functionalized by (a) O, (b) F, and (c) OH. Color code: Sc pink, C brown, O red, F blue, and H yellow.

Figure 2

Band structures with orbital weights.

Figure 3

Seebeck coefficients and electrical conductivities.

Figure 4

Thermoelectric power factors and electronic thermal conductivities.

Figure 5

Phonon dispersion relations. Additional optical branches appear at higher energy for OH functionalization.

Figure 6

Lattice thermal conductivities, room-temperature anharmonic scattering rates (black, red, blue, and green color refers to the ZA, TA, LA, and optical branches, respectively), and cumulative lattice thermal conductivities.

Figure 7

Figures of merit.