Thermoelectric properties of cotton fibrous structures knife-coated with PU/PEDOT:PSS/GNP

The present study reports the functionalisation of cotton woven (CO) textiles with polyurethane (PU)-based coatings containing graphene nanoplatelets (GNPs) and PEDOT:PSS, aiming to develop thermoelectric textiles. A fixed concentration (5 % (w/v)) of GNPs is combined with five contents of PEDOT:PSS (0-2.5 % (w/v)) to tailor the thermoelectric performance. Structural, morphological and thermal analyses confirm uniform coating penetration into the textile and a good dispersion of the GNPs, as evidenced by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The incorporation of the GNPs enables electrical percolation, therefore yielding the larger electrical conductivity ( σ ), of 0.62 ± 0.18 S/m (when no PEDOT:PSS is present), while the addition of PEDOT:PSS reshapes charge transfer through energy-filtering effects, increasing the Seebeck coefficient ( S ) (to a maximum value of 18.3 ± 1.1 μV/K, at 2 % (w/v) PEDOT:PSS), despite a reduction in σ . All functional coated samples exhibit p-type thermoelectric behaviour and maintain small thermal conductivity ( κ ), with values ranging from 0.008 to 0.015 W/(m.K). The highest figure of merit ( ZT ) of (3.4 ± 0.9) × 10 -6 at 300 K was obtained for the formulation containing 2.5 % (w/v) PEDOT:PSS, reflecting a better balance between σ , S and κ . Although the thermoelectric performance remains modest, the results demonstrate the potential of GNP/PEDOT:PSS-PU-coated textiles for low-power energy harvesting or thermal sensing applications.