ABSTRACT
Efforts to produce graphene started from the preparation of graphitic oxide in 1859 by Brodie [9]. Until now, various methods have been developed to fabricate, grow, or synthesize graphene. Weak van der Waals interactions between the adjacent graphene layers exist to bind them in the bulk graphite [10]. Hence the single-layer graphene can be prepared from the well-known top-down approach of micromechanical exfoliation of graphite (also named as the “Scotch tape” method) [3]. Besides, versatile bottom-up approaches can be adopted to grow graphene sheets. Chemical vapor deposition (CVD) can grow single-or few-layer graphene sheets on metal substrates, such as Ni [11,12], Cu [13-15], and Ru [16]. Afterwards, the as-grown graphene can be transferred to arbitrary substrates. The epitaxial growth of graphene can also be achieved on insulating substrates, such as SiC [17,18]. Moreover, graphene can be prepared through the synthesis from organic precursors [19,20]. However, one of the most commonly used and developed method to acquire graphene is the chemical reduction of graphene oxide (GO), which is synthesized by oxidation and exfoliation of graphite [21−26]. Fabrication of GO by the Hummers method involves the treatment of graphite with strong acids and oxidizers, such as sulfuric acid, nitric acid, potassium permanganate, and potassium chlorate [27−35]. Graphene thus can be produced by chemical reduction of GO with hydrazine [21−26, 36−38], dimethyhydrazine
[39], hydroquinone [40], NaOH or KOH [41], vitamin C [42], or bovine serum albumin (BSA) [43]. Table 11.1 summarizes the advantages and disadvantages of the above mentioned four primary methods to produce graphene. In addition to chemical reduction of GO, there are many other methods to reduce GO, such as thermal reduction via the high-temperature deoxygenating process [44−46], hydrothermal dehydration of exfoliated GO using supercritical water as the reducing agent [47], electrochemical reduction method [48−50], photochemical reduction [51,52], etc. Table 11.1 Advantages and disadvantages of four primary methods to produce graphene
Method Advantages DisadvantagesMicromechanical exfoliation of graphite Produces high-quality graphene Low throughput, low yieldCVD/Epitaxial growth Produces high-quality and large-area graphene Requires stringent conditions and careful control for uniform growth of grapheneChemical reduction of GO Low cost, large-amount production Produces poor-quality graphene with extensive modification of grapheneBottom-up synthesis from organic precursors
Size controllable synthesis of graphene Difficult to yield large-scale graphene with narrow size distribution and almost impossible to avoid side reactions 11.3 Introduction to Graphene OxideAs a precursor to synthesize graphene (also referred to as reduced graphene oxide, rGO), GO has a graphene-like structure but with a range of oxygen functional groups. The most accepted model for its structure is the Lerf−Klinowski model [53], which describes that GO has a layered structure containing abundant epoxy and hydroxyl groups on the basal planes and a few carbonyl and carboxyl groups at the edges. Subsequently, Gao et al. proved that there are five-and six-membered-ring lactols on the periphery of GO and added them into the structural model (Fig. 11.1) [54].
