High-Efficiency Production of Large-Size Few-Layer Graphene Platelets via Pulsed Discharge of Graphite Strips

1. Introduction

Graphene, firstly synthesized by Noveselov et al. [1] in 2004, has been proved as a wonderful future material with plenty of applications [2,3,4,5,6,7,8]. As a typical two-dimensional material, its particular atom-thick graphitic layer structure consisting of carbon atoms packed into a honeycomb lattice possesses various unique properties compared with other carbon nanomaterials [9], including outstanding thermal transport property [10,11], superconductivity [12,13], mechanical properties [5,6,14], optical properties [15,16], electronic properties [1,4,17], etc. A great deal of research has suggested multiple applications of graphene in areas such as field effect transistors [1,18], sensors [19,20], metal-free electrodes [21,22], energy storage [23], biomedical applications [24], etc. In addition, the applications of graphene materials also depend on their specific morphology [4,23], lateral dimension [25,26,27], and quality [25,27]. In much of the research conducted on graphene, one central focus is to synthesize large-size graphene materials for a higher potential application in the areas of electronics, solar energy devices, and mechanical structures [28,29,30]. For example, Ruse et al. [25] demonstrated that graphene with a large size increases the hydrogen storage of Mg/graphene nanocomposite by bridging Mg nanoparticles. Xu et al. [29] also employed the graphene at a size of 50 μm–1 mm grown on Ni film substrate to improve the light transmittance in the mid-infrared (MIR) bandwidth of HgCdTe infrared detector with low cost. Additionally, Zhang et al. [31] synthesized large area uniform graphene film consisting of 1–30 μm graphene platelets to replace indium tin oxide (ITO) as flexible, transparent conductive film.

Various methods have been reported to synthesize graphene materials [9,32,33,34,35,36] including mechanical exfoliation method, oxidation reduction method, chemical vapor deposition (CVD) method, liquid-phase exfoliation method, arc-discharge method, electrochemical exfoliation method, detonation method, pulsed wire discharge method, interlayer catalytic exfoliation, etc. Among them, several methods, including oxidation reduction method, CVD method, and interlayer catalytic exfoliation, have been reported to prepare large-size graphene. Su et al. [37] obtained ultra large single-layer reduced graphene oxide (up to millimeter size) using oxidation reduction method (Hummer’s method). In this study, natural graphite flakes with an average size of 3–5 mm were oxidized by a mixture of concentrated H₂SO₄, P₂O₅ and K₂S₂O₈, exfoliated by stirring with addition of KMnO₄,...