Recycled carbon fibre/Bi₂Te₃ and Bi₂S₃ hybrid composite doped with MWCNTs for thermoelectric applications

In this study, a cost-effective thermoelectric generator was developed from recycled carbon fibre (RCF) composites incorporated with multi-walled carbon nanotubes (MWCNT) doped bismuth telluride (Bi₂Te₃) and bismuth sulphide (Bi₂S₃). A facile approach utilising hot compression and brushing was used to prepare a cost-effective inorganic RCF thermoelectric composite with varying content of MWCNT ranging from 0.05 to 0.20 wt%. This work investigated the effect of doping MWCNT in Bi₂Te₃ and Bi₂S₃ matrix and its corresponding effect on thermoelectric, morphological, structural and thermal properties of RCF thermoelectric composite. The thermoelectric properties of RCF composites were optimised at 0.10 wt % (1.044 μW K⁻²m⁻¹) and 0.15 wt% (0.849 μW K⁻²m⁻¹) of MWCNT for doped Bi₂Te₃ and Bi₂S₃ respectively. The addition of MWCNT reduced the difference in power factor between RCF-Bi₂Te₃ and RCF-Bi₂S₃ from 52% to 19%. The presence of MWCNT in the Bi₂S₃ matrix overcame the high resistivity of Bi₂S₃ and improved its thermoelectric properties as MWCNT provided a conductive pathway for efficient electron transfer. Thus, MWCNT doped Bi₂S₃ RCF composites is an alternative to telluride free thermoelectric generators.