Electronic, Optical and Thermoelectric Properties of Two-Dimensional Molybdenum Carbon Mo2C-MXenes

We investigate the structural, electronic, optical, and thermoelectric properties of three compositions of Mo2C-MXenes (Mo2CF2, Mo2C(OH)2, and Mo2CO2) from monolayer to multilayer by first principles calculation within Density Functional Theory (DFT) and Boltzmann transport theory. Firstly, the atomic structures of Mo2C-MXenes are optimized, and their respective structures are created with comparative research. Secondly, their electronic band structures and optical properties are studied in detail. The estimation of the bandgap energy of Mo2C-MXenes with its functionalization reveal that most Mo2CF2 and Mo2C(OH)2 layers are semiconductors, while Mo2CO2 behaves as a metal. The electrical and optical properties can be altered by controlling the on-surface functional groups and the number of layers. Computation of the thermoelectric (TE) properties of Mo2C-MXenes reveals that, upon heating to 600 K, Mo2CF2 and Mo2C(OH)2 exhibit a high Seebeck coefficient and a relatively high electrical conductivity. The Seebeck coefficient reaches ~400 µV K−1 at room temperature for all layers of Mo2CF2 MXenes. Our results prove that Mo2CF2 is considered a promising material for thermoelectric devices, while Mo2CO2 does not possess better thermoelectric performance. Mo2C-MXenes from monolayer to multilayer have outstanding properties, such as flexible bandgap energy and high thermal stability, making them promising candidates for many applications, including energy storage and electrode applications.