Cu2Se/MXene (Ti3C2Tx) composite achieved ultra-low thermal conductivity and enhanced thermoelectric performance

Due to the significant mismatch in phonon density of states between carbon (C) and Cu${}_2$Se, the thermal conductivity of Cu${}_2$Se can be notably enhanced by incorporating low-dimensional carbon-based materials. This study propose an innovative approach where two-dimensional MXene material Ti${}_3$C${}_2$T${}_x$ is introduced into Cu${}_2$Se, creating numerous Cu${}_2$Se/MXene heterogeneous interfaces within the matrix. These interfaces induce high-density dislocations, which enhance multi-scale phonon scattering efficiency. Consequently, they significantly reduce lattice thermal conductivity across the entire temperature range tested. Additionally, the heterogeneous interfaces facilitate energy filtration, selectively filtering out low-energy carriers and thereby optimizing the high intrinsic carrier concentration of Cu${}_2$Se to a certain extent. Finally, the total thermal conductivity of the Cu${}_2$Se/0.4 wt% Ti${}_3$C${}_2$T${}_x$ sample at 795 K is markedly lower at 0.27 Wm⁻¹K⁻¹ compared to the average level of Cu${}_2$Se materials. As a result, the $Z{T}_{max}$ reaches 2.11, reflecting a 109% enhancement compared to pristine Cu${}_2$Se.