Bridging graphene for films with superior mechanical and electrical performance for electromagnetic interference shielding

Macroscopic films assembled from graphene sheets could be ideal for lightweight and flexible electromagnetic interference shielding applications if the excellent mechanical strength and electrical conductivity of individual graphene can be replicated on the macroscale. However, in practice, a large performance gap remains between individual graphene and graphene-based macroscopic films. In this work, we report macroscopic graphene-based films with high mechanical strength and electrical conductivity (1.70 ​± ​0.05 ​GPa and 1170 ​± ​60 ​S ​cm⁻¹) obtained by introducing a covalent conjugating aromatic amide group to bridge graphene edges. The bridging was achieved by reacting a doctor-bladed GO film with 1,2,4,5-benzenetetraamine hydrochloride followed by chemical reduction. Impact load tests demonstrated efficient stress transfer in these films, with stress spread uniformly well beyond the impact area. This is in sharp contrast to previously reported films, which showed the immediate initiation of cracks followed by crack extension in random directions. Our conducting films achieved a shielding effectiveness of 114.1 ​dB for a 120 ​μm thick film, and the specific shielding effectiveness was calculated to be 67.9 ​dB ​cm³ g⁻¹, which significantly exceeds those of currently known shielding materials as well as graphene films synthesized under similar conditions without thermal annealing. Owing to the graphene films’ mechanical robustness, the shielding performance was maintained even after repeated folding.