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Wang et al. Soft Sci 2023;3:34 https://dx.doi.org/10.20517/ss.2023.25 Page 19 of 26

©
Figure 14. (A) TE properties of two-dimensional molybdenum-based MXenes. Reproduced with permission from Ref [22] . Copyright
2017. American Chemical Society; (B) The schematic structure diagrams of Ti C T /SWCNT, Ti C T -SWCNT-Ti C T , and SWCNT-
3
2 x
3
2
x
2 x
3
©
Ti C T -SWCNT films. Reproduced with permission from Ref [116] . Copyright 2020. John Wiley and Sons; (C) Schematic demonstration
2 x
3
©
of the preparation process of Bi Te Se /Ti C T composites. Reproduced with permission from Ref [117] . Copyright 2022. Elsevier. TE:
2 x
3
2
2.7
0.3
Thermoelectric; SWCNT: single-walled carbon nanotube.
2
61.70 μW/mK were fabricated using a facile vacuum filtration technique.
MXenes have attracted widespread attention as two-dimensional materials containing transition metal
carbides and nitrides. In 2017, Kim et al. employed vacuum-assisted filtration to prepare three free-standing
MXenes (Mo CT , Mo TiC T , and Mo Ti C T ) films [Figure 14A] , which exhibit n-type Seebeck
[22]
2
x
2
x
3
2
2
2
x
coefficients and high electrical conductivity upon heating to 800 K. For the Mo TiC T MXene, the power
2 x
2
factor reached 3.09 × 10 W/mK at 803 K. Then, Ding et al. reported that a practical heterostructure design
-4
2
could effectively improve the TE performance of MXenes [Figure 14B] . Layered composite films with
[116]
2D-3D sandwich structures consisting of 2D MXenes and 1D SWCNTs were prepared by vacuum-assisted
filtration. The Ti C T -SWCNTs-Ti C T film displayed considerable electrical conductivity of 750.9 S/cm
3
2 x
3
2 x
and an enhanced Seebeck coefficient of -32.2 μV/K. Compared to Ti C T /SWCNT films with interlaced
2 x
3
structures, the Ti C T -SWCNTs-Ti C T film shows a higher power factor, 25 times higher than that of
3
2 x
2 x
3
Ti C T films. Recently, Diao et al. prepared the Bi Te Se /Ti C T composite material by simple mixing,
3 2 x
0.3
2.7
2
2 x
3
vacuum-assisted filtration, and hot pressing [Figure 14C] . Excellent TE conversion (a ZT value of 1.2
[117]
listed in Table 5) and high-performance electromagnetic interference shielding were simultaneously
achieved.
TERNARY COMPOSITE TE MATERIALS
Introducing carbon materials with high electrical conductivity into inorganic TE materials fillers with high