Preparation of high-quality graphene sheets and their applications in highly conductive papers and a high-performance electromechanical actuator

Abstract

The increasing demand for graphene has called for the requirement of a new method that would produce graphene on a large scale without the occurrence of significant damage. In this paper, we report a simple and facile exfoliation method for the production of a stable dispersion of high-quality graphene sheets using the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF₄). Subsequently formed graphene papers exhibited the electrical conductivity value of 1800 S cm⁻¹ in conducting graphene films after being air-dried. The suspensions of the exfoliated graphene were derived from crystalline graphite and found to be stable for more than one month. Successful intercalation of the ionic liquid between the graphite interlayers through liquid-state diffusion of imidazolium cations was confirmed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The chemical composition demonstrates that the exfoliated graphene sheets preserve their pristine properties without any degradation. To demonstrate the diverse functionality of the exfoliated graphene sheets, a graphene-based electromechanical actuator was constructed. The high-performance “dry” graphene-based actuator showed a large bending movement of up to 15 mm in the strip response to an applied bias voltage of 2 V under ambient conditions. The overall results indicate that this solution-based method can be a scalable and low-cost route to the mass production of high-quality graphene. Because the process is completely solvent-based, these unique papers can be readily fabricated and should create tremendous opportunities in the fields of graphene-based electronics, printable electrochemical sensors, and energy storage.