The highly electrically conductive graphene papers prepared from graphene oxide have shown promising perspectives in flexible electronics, electromagnetic interference (EMI) shielding, and electrodes. To achieve high electrical conductivity, the graphene oxide precursor usually needs to be graphitized at extremely high temperature (~ 2,800 °C), which severely increases the energy consumption and production costs. Here, we report an efficient catalytic graphitization approach to fabricate highly conductive graphene papers at lower annealing temperature. The graphene papers with boron catalyst annealed at 2,000 °C show a high conductivity of ~ 3,400 S·cm^–1, about 47% higher than pure graphene papers. Boron catalyst facilitates the recovery of structural defects and improves the degree of graphitization by 80%. We further study the catalytic effect of boron on the graphitization behavior of graphene oxide. The results show that the activation energy of the catalytic graphitization process is as low as 80.1 kJ·mol^–1 in the temperature ranges studied. This effective strategy of catalytic graphitization should also be helpful in the fabrication of other kinds of highly conductive graphene macroscopic materials.

Flexible wearable electronics, when combined with outstanding thermoelectric properties, are promising candidates for future energy harvesting systems. Graphene and its macroscopic assemblies (e.g., graphene-based fibers and films) have thus been the subject of numerous studies because of their extraordinary electrical and mechanical properties. However, these assemblies have not been considered suitable for thermoelectric applications owing to their high intrinsic thermal conductivity. In this study, bromine doping is demonstrated to be an effective method for significantly enhancing the thermoelectric properties of graphene fibers. Doping enhances phonon scattering due to the increased defects and thus decreases the thermal conductivity, while the electrical conductivity and Seebeck coefficient are increased by the Fermi level downshift. As a result, the maximum figure of merit is 2.76 × 10^-3, which is approximately four orders of magnitude larger than that of the undoped fibers throughout the temperature range. Moreover, the room temperature power factor is shown to increase up to 624 μW·m^-1·K^-2, which is higher than that of any other material solely composed of carbon nanotubes and graphene. The enhanced thermoelectric properties indicate the promising potential for graphene fibers in wearable energy harvesting systems.

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.

Nacre is a lightweight, strong, stiff, and tough material, which makes it a mimicking object for material design. Many attempts to mimic nacre by various methods resulted in the synthesis of artificial nacre with excellent properties. However, the fabrication procedure was very laborious and time-consuming due to the sequential steps, and only limited-sized materials could be obtained. Hence, a novel design enabling scalable production of high-performance artificial nacre with uniform layered structures is urgently needed. We developed a novel wet-spinning assembly technique to rapidly manufacture continuous nacremimic graphene oxide (GO, brick)-sodium alginate (SA, mortar) films and fibers with excellent mechanical properties. At high concentrations, the GO-SA mixtures spontaneously produced liquid crystals (LCs) due to the template effect of GO, and continuous, 6 m long nacre-like GO-SA films were wet-spun from the obtained GO-SA liquid crystalline (LC) dope with a speed of up to 1.5 m/min. The assembled macroscopic GO-SA composites inherited the alignment of the GO sheets from the LC phase, and their mechanical properties were investigated by a joint experimental-computational study. The tensile tests revealed that the maximum strength (σ) and Young's modulus (E) of the obtained films reached 239.6 MPa and 22.4 GPa, while the maximum values of σ and E for the fibers were 784.9 MPa and 58 GPa, respectively. The described wet-spinning assembly method is applicable for a large-scale and fast production of high-performance continuous artificial nacre.