# Facile Preparation of Multilayered Graphene with CO\({}_{2}\) as a Carbon Source
## 1 Introduction  
Graphene, the two-dimensional sp\({}^{2}\)-hybridized carbon, has undoubtedly become one of the most exciting current topics of research. It is widely considered to have a series of unusual characteristics, especially its thermal conductivity (-3000 Wm\({}^{-1}\)K\({}^{-1}\)) and mechanical stiffness (-1060 GPa), which may rival the remarkable in-plane values of graphite [1; 2; 3; 4; 5; 6; 7]. Moreover, their fracture strength should be comparable to that of carbon nanotubes for similar types of defects [8]. In addition, some studies have shown that individual graphene sheets have outstanding electronic transport characteristics [9]. Since the monolayer graphene was first obtained by [PERSON] and co-workers using the tape method [10], there has been increasing attention towards methods of such material preparation. The commonly applied methods include the micromechanical or chemical exfoliation of graphite, epitaxial growth on silicon carbide (SiC), chemical vapor deposition (CVD), as well as reduction of graphene oxide (GO) via chemical, electrochemical, thermal, or photocatalytic methods [11; 12; 13; 14; 15; 16; 17; 18]. Among the above methods, a major focus of experimental research has been concentrated on the development of low-pollution preparation routes, enabling environmentally friendly production. More and more reports involve graphene preparation with a particular emphasis on a low energy cost and less pollution. For example, [PERSON] et al. [19] developed a method consuming less energy by introducing pregraphitic materials, new alternatives to graphite, for producing graphene, which exhibited similar characteristics to those obtained from graphite, but with less energy consumption as their production required lower temperatures (not higher than 1100 \({}^{\circ}\)C). After that, [PERSON] and co-workers [20] reported a facile and mild route to synthesize free-standing and monolithic 3D functionalized graphene with biomass source-glucose as the carbon source, which is environmentally benign and low cost. In summary, much progress has been made on graphene preparation with an environmentally friendly and low resource-consuming route. At present, carbon dioxide, mainly generated by fuel combustion, is the major gas blamed for causing the greenhouse effect. Nevertheless, stopping fuel combustion completely may not be achieved in the short-term. Therefore, rational utilization of carbon dioxide in the atmosphere is quite real and is of great importance. If it can be used as a carbon source for products with high value, it can not only reduce CO\({}_{2}\) emissions, but also obtain materials with high value. Some researchers have already worked on exploiting CO\({}_{2}\) for high-value products, such as carbon fibers [21], lithium battery [22], and formic acid [23]. Among them, [PERSON] et al. [24] produced multilayered graphene with carbon dioxide, which has achieved much attention. Multilayered graphene, which can be produced on a large scale, shows excellent performance, especially on thermal conductivity and mechanical stiffness [25; 26; 27; 28]. It is widely used in sensors [29], electrodes [30; 31], and other areas [32; 33]. For example, [PERSON] et al. reported a fabrication method for hydrogen sensing using a multilayered graphene, which opened up the possibility of using multilayered graphene in molecular sensing applications [29]. [PERSON] et al. used multilayered graphene to prepare electrodes by using in-situ exfoliation of graphite, considering that multilayered graphene is easier to be obtained at a large scale by exfoliation methods than graphene monolayer [31]. [PERSON] et al. demonstrated an epidermal electronic skin with good sensitivity and stability based on multilayered graphene [33]. In summary, multilayered graphene has indispensable applications in many fields and to some extent, it is superior to the graphene monolayer.