## 2 Graphene and Graphene-Related Materials  
### Overview on Graphene and Related Materials  
Graphene is ideally a single plane of graphite with no defect sites. Carbon atoms of the graphene elementary cell are bonded through three \(\sigma\) bonds with the p orbitals perpendicular to the sp\({}^{2}\) plane. This structure allows the total delocalization of the \(\pi\) bond on the graphene plane. Consequently, the \(\pi\)-electrons freely move alongside the graphene plane [34; 35; 36]. This is the reason of its high electrical conductivity and carrier rate [37]. The astonishing properties of neat graphene are counterbalanced by the difficulties in handling it and by its scarce availability [38]. As a matter of fact, plenty of literature uses the term graphene to define nanographite and a few layered materials [39; 40]. In order to overcome the issues related to the use of real neat graphene, several materials have been proposed. The first alternative is graphene oxide (GO). GO is an oxidized graphene derivative rich in oxygen functionalities [41]. The main residual groups on the GO basal lattice are epoxide and hydroxyl groups, while carbonyl and carboxylic ones are more abundant on the edges. Contrary to pure neat graphene, GO's structure is deeply affected by its preparation methodologies. The production of GO started more than fifteen decades ago with the chemical reactivity of graphite studied by [PERSON] in 1859 during the measurements to identify the atomic weight of carbon [42]. In his experiments, [PERSON] oxidized graphite by using a mixture of nitric acid and potassium chlorate for long times, up to days. He obtained a light-yellow powder characterized by brilliant transparent flakes. [PERSON] called it graphitic acid, but nowadays that material is known as GO. Fifty years later, [PERSON] reported another methodology for the production of \"graphitic acids\" by using a highly acidic solution of KClO\({}_{3}\)[43]. A further approach was reported by [PERSON] and [PERSON] in the mid-twentieth century [44]. In this case, graphite was treated with a sulphuric acid solution of potassium permanganate and sodium nitrate. Nowadays, [PERSON] methods is mostly used to produce graphite oxide in laboratories all around the world. Nonetheless, all three methods are still used to produce GO with different features. An exhaustive study was conducted by [PERSON] and co-workers [45] by describing the different properties of reduced GO (rGO) obtained from GO. The authors clearly explain the effect of different oxygen-containing functionalities on the final properties of rGO itself due to the different production methods. Since different methods are used to synthesize GO, its composition and non-stoichiometric structure are highly based on the production details [46]. Consequently, numerous studies have proposed several structures for GO, namely the Hofmann, Ruess, Scholz-Boehm, Nakajima-Matsuo, Lerf-Klinowski, and Szabo models [47], as shown in Figure 1b-g. The scientific community generally agreed on the Lerf-Klinowski as the more realistic structure to describe GO as proved by a plethora of evidences [49]. Based on this model, defects such as cracks, wrinkles, holes, and impurities are principally due to the oxidation process. GO is not the only graphene derivative that attracted the scientists' attention. The above mentioned rGO is the rising star in the field of graphene research [50]. rGO is produced through a reduction process of GO by using several reductive agents [51; 52]. Through reductive process, the oxygenated functional groups of GO are eliminated to form rGO with a carbon to oxygen (C/O) ratio in the range from 12.5 to 0.4 wt.% [53]. Due to their high surface area and stability, they represent the new generation of nanostructured carbon support for plenty of catalytic applications. The production of new materials by using graphene and graphene-derived materials could be performed by using several approaches based on targeted application.