## 3 Results and Discussion  
### Characteristics of the Graphene Materials  
XRD is a powerful tool to evaluate the interlayer changes of graphene-based materials. The XRD patterns of G\({}_{10}\), G\({}_{100}\), G\({}_{325}\), GO\({}_{10}\), GO\({}_{100}\), and GO\({}_{325}\) samples are shown in Figure 1. The G samples presented the characteristic diffraction peak corresponding to pristine graphite (002) reflection at 2\(\thicksim\)26\({}^{\circ}\)[10]. A downshift for (002) reflection peak to 20\(\sim\)15\({}^{\circ}\) after the oxidation treatment was observed for all the GO samples. It indicates that a successful oxidization of all G samples was achieved [8]. The distance between layers (d\({}_{(002)}\)) increased from 0.33 nm (for G) to 0.57 nm (for GO samples), which is due to the presence of interlayered species incorporated during the oxidation of graphite [25]. The morphology of the GOs was observed by SEM. Figure 2 shows representative images of the GO samples. The analysis of the particle size distribution based on a minimum of 200 particles shows that the average particle sizes of GO\({}_{10}\), GO\({}_{100}\), and GO\({}_{325}\) samples are 86, 38, and 25 um, respectively. Slow heating rates were selected to be evaluated during the exfoliation process of GOs, since fast heating rates produce more wrinkled sheets [25]. Thus, small heating rates are fast enough to produce an effective expansion allowing the exfoliation and minimizing the distortion of the graphene sheets. It is known that oxygen groups decompose at high temperatures, reducing the number of reactive sites for N doping [34], and that high annealing temperatures (\(>\)700 \({}^{\circ}\)C) could break C-N bonds in the NrGO materials leading to a low doping level [40]. So, temperatures up to 700 \({}^{\circ}\)C were used in the thermal treatments applied to the GO samples. Table 1 compiles the main characteristics of the non-doped and N-doped reduced graphite oxides obtained. Firstly, the GO\({}_{325}\) sample was submitted in both inert atmosphere and atmosphere with the presence of ammonia to five different thermal ramps described in the experimental section. Application of the BET method to N\({}_{2}\) adsorption isotherms (these type IV isotherms were displayed in the Figure S1 of the Electronic Supplementary Information, ESI) measured over the GO\({}_{325}\)-derived non-doped and N-doped reduced graphene oxides gave surface area (S\({}_{\text{BET}}\)) values ranging from 667 to 867 m\({}^{2}\) g\({}^{-1}\) for the different rGO\({}_{325}\) samples and from 427 to 492 m\({}^{2}\) g\({}^{-1}\) for the NrGO\({}_{325}\) samples. These obtained \(S_{\text{BET}}\) values are significantly lower than the theoretical value calculated for a single layer of graphene (2630 m\({}^{2}\) g\({}^{-1}\)) [8]. This finding indicates the piling up of graphene layers and the formation of a few-layer graphene structure for both rGO and NrGO. However, these values are much higher than the values previously reported using thermal exfoliation to produce rGO [36; 38] and NrGO [10]. From the results shown in Table 1, it can be seen that ramp 3 for non-doped reduced graphene oxide (rGO\({}_{325}\)) and ramp 4 for N-doped reduced graphene oxide (NrGO\({}_{325}\)) led to reduced materials having an enhanced \(S_{\text{BET}}\). The ramps used for the exfoliation of GO\({}_{10}\) and GO\({}_{100}\) were selected based on these results. Thus, the ramp used for the preparation of rGO\({}_{10}\) and rGO\({}_{100}\) was ramp 3, and for NrGO\({}_{10}\) and NrGO\({}_{100}\) was ramp 4. A significant and gradual decrease of the surface area values was observed for rGO and NrGO sample series as the size of starting graphite increases. These findings are coherent with the tendency  
Figure 1: XRD patterns of graphene (G\({}_{\text{m}}\)) and graphite oxide (GO\({}_{\text{m}}\)), where m indicates the mesh samples used. previously reported for non-doped graphene by [PERSON] et al.