Energy band gaps and novel thermoelectric properties of two-dimensional functionalized Yttrium carbides (MXenes)

The electronic and thermoelectric properties of two-dimensional Yttrium carbide MXenes (Y2CT2, T = F, Br, OH, H), Y2CClH and Y2CFH are studied by first-principle calculations within the density functional theory and Boltzmann theory respectively. The results of the electronic structure revealed that the MXenes possess energy gaps (0.47 - 1.17eV) making them semiconductors. At the temperatures T = 100 K and 400 K, the MXenes attain high and moderate figures of merit and Seebeck coefficients near the band edges with Y2CH2 having the largest value of ZT = 0.97, which can be compared to 10% Carnot cycle efficiency. Generally, the MXenes support chemical stability owing to the negative values of the formation energies which may indicate the feasibility of fabricating them experimentally. Our results indicate that the Yttrium carbide-based MXenes are potential thermoelectric materials at low and moderate temperatures.