Electrical, thermal and thermoelectric properties of Ti3C2Tx films: uncovering the significant role of water molecules

Abstract

Ti₃C₂T_x has been developed and studied for years. However, systematic research on the physics of Ti₃C₂T_x films, especially the thermophysics, is still lacking. In this work, we comprehensively characterized the electric and thermal transport and thermoelectric effects of Ti₃C₂T_x films in the temperature range of 120 to 300 K and deeply studied the influence of water molecule adsorption on the above physical processes in the humidity range of 0% to 80%. The electrical and thermal conductivity and Seebeck coefficient of Ti₃C₂T_x films at room temperature and 0% humidity are 8200 S m⁻¹, 56 W m⁻¹ K⁻¹ and −8.96 μV K⁻¹. It is found that water molecules adsorb on Ti₃C₂T_x nanoflakes through hydrogen bonds, with a binding energy of 0.2 eV. The adsorption of water molecules employed scattering sites, which reduced carrier mobility, without changing the carrier concentration, Fermi-level and Seebeck coefficient. Gas and water molecules are significant in the thermal transport of Ti₃C₂T_x films, resulting in a big difference of thermal conductivity under vacuum and in air. The adsorption of water molecules enhances the phonon coupling between Ti₃C₂T_x nanoflakes and thus the thermal conductivity of the films. Our work deepens our understanding of Ti₃C₂T_x films and provides theoretical references for their applications.