Assessment on Lattice Thermal Transport Properties of Functionalized MXene Structures

The newest members of 2D transition metal carbides and nitrides, so-called MXenes, receive increasing attention due to their novel electronic and thermal properties that can be tuned for specific applications. Electronic... [ view full abstract ]

The newest members of 2D transition metal carbides and nitrides, so-called MXenes, receive increasing attention due to their novel electronic and thermal properties that can be tuned for specific applications. Electronic properties and dynamical stabilities of various MXene structures have been investigated by different research groups, however, only a very few of them focused on thermoelectric performance of the semiconductor MXene materials. In this study, we investigated the lattice thermal conductivity and Seebeck coefficients of oxygen terminated M₂CO₂ (M=Ti, Zr, Hf, Sc) MXenes in two different configurations (MD-II, MD-III) using Density Functional Theory and the Phonon Boltzmann Transport Theory. Investigating the structural and compositional variety provides us additional degrees of freedom for modulating physical and chemical properties of MXenes. We found that within MD-III configurations, thermal conductivity can be lowered by a factor of three for Zr₂CO₂ and by a factor of two for Ti₂CO₂ and Hf₂CO₂ in comparison to MD-II configurations. We also obtained that Seebeck coefficients are larger approximately by a factor of three for Ti₂CO₂ and by a factor of 1.1 for Zr₂CO₂ and Hf₂CO₂ in the MD-III configurations compared to MD-II configurations. Our study demonstrated that Ti₂CO₂ and Zr₂CO₂ in MD-III configurations are promising candidates for next-generation thermoelectric applications thanks to their low thermal-conductivities and large Seebeck coefficients.