Systematic characterization of transport and thermoelectric properties of a macroscopic graphene fiber

Graphene, a two-dimensional material with extraordinary electrical, thermal, and elastic performance, is a potential candidate for future technologies. However, the superior properties of graphene have not yet been realized for graphenederived macroscopic structures such as graphene fibers. In this study, we systematically investigated the temperature (T)-dependent transport and thermoelectric properties of graphene fiber, including the thermal conductivity (λ), electrical conductivity (σ), and Seebeck coefficient (S). λ increases from 45.8 to 149.7 W·m^–1·K^–1 and then decreases as T increases from 80 to 290 K, indicating the boundary-scattering and three-phonon Umklapp scattering processes. σ increases with T from 7.1 × 10⁴ to 1.18 × 10⁵ S·m^–1, which can be best explained by the hopping mechanism. S ranges from–3.9 to 0.8 μV·K^–1 and undergoes a sign transition at approximately 100 K.