## 3 Results  
### Effect of the Vitamin C (VC) Amount on Textural Properties and Hydrophobicity  
Figure S2 shows digital photos of the rGOAs. The as-prepared samples exhibit different macroscopic appearances with and without VC. When VC is added, the rGOAs exist as a monolithic bulk with a stable cylindrical shape, as shown in Figure S2b-d. By contrast, the rGOA-0 yields only loose black mass powder (Figure S2a). It indicates that VC is beneficial to the fabrication of the rGOAs, yielding a three-dimensional monolithic  
porous architecture of aerogel via \(\pi\)-\(\pi\) interactions, hydrophobicity, hydrogen bonds, and Van der Waals forces [20; 31]. In addition, the amount of VC has a positive effect on the structure and functionality of the rGOAs. To assess the textural properties of IGGO and rGOAs, textural parameters (\(S_{\text{BET}}\), \(V_{\text{tot}}\), \(D_{\text{aver}}\), and contact angle) are listed in Table 1. As evident from Table 1, the rGOAs exhibit a significant improvement in the textural properties, where rGOA-1 has the highest values of \(S_{\text{BET}}\) and \(V_{\text{tot}}\). For comparison, we chose the original samples of IGGO, rGOA-0 (without VC) and rGOA-1 (with highest specific surface area) to perform the rest of the experiments. Figure 1a,b) shows the nitrogen adsorption-desorption isotherms and the pore size distribution of IGGO and two representative rGOA composites (i.e., rGOA-0 and rGOA-1). As shown in Figure 1a, from N\({}_{2}\) adsorption-desorption isotherms, rGOA-1 presents a IUPAC type IV isotherm with a type H3 hysteresis loop [38], suggesting the existence of an external surface and mesopores [30]. On the other hand, IGGO and rGOA-0 have a much smaller nitrogen adsorption volume than rGOA-1, exhibiting type III isotherms, with nearly non-porous structure [21]. Remarkably, rGOA-1 exhibits narrower mesopores than IGGO and rGOA-0, as shown in Figure 1b. According to the literature [30], a narrower mesoporous range is favorable for the adsorption of L2. The photos measuring contact angles are shown in Figure S3. The contact angle measurements of the adsorbents are listed in Table 1. The hydrophobicity of the rGOAs is stronger than that of IGGO, which might be explained by the removal of oxygen-containing groups of IGGO upon the reduction. In addition, rGOA-1 has the highest contact angle of 143.8\({}^{\circ}\), showing super-hydrophobicity. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR), and Raman Analyses of Industrial-Grade Graphene Oxide (IGGO), rGOA-0, and rGOA-1  
SEM micrographs of IGGO, rGOA-0, and rGOA-1 are shown in Figure 2. For IGGO, they confirm a certain degree of aggregation of multilayered graphene sheets (Figure 2a,b). For rGOA-0, a few nanosheets are stacked and entangled, exhibiting no formation of a crosslinked structure (Figure 2c,d), perhaps due to insufficient hydrothermal self-assembly [30]. In particular, rGOA-1 shows a rich 3D porous network structure \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**adsorbent** & \(S_{\text{BET}}\) (\(\text{m}^{2}\) g\({}^{-1}\)) & \(V_{\text{tot}}\) (\(\text{cm}^{3}\) g\({}^{-1}\)) & \(D_{\text{aver}}\) (nm) & **Contact Angle (\({}^{\circ}\))** \\ \hline IGGO & 7.4 & 0.23 & 13.18 & 76.6 \\ rGOA-0 & 19.1 & 0.39 & 10.30 & 119.9 \\ rGOA-0.5 & 86.8 & 0.71 & 9.20 & 135.1 \\ rGOA-1 & 137.9 & 0.88 & 5.08 & 143.8 \\ rGOA-2 & 76.1 & 0.65 & 8.76 & 132.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of industrial-grade multilayer graphene oxide (IGGO) and reduced graphene-oxide aerogels (rGOAs). Figure 1: The nitrogen adsorption–desorption isotherms (**a**) and pore size distribution (**b**) by IGGO, rGOA-0, and rGOA-1. (Figure 2e,f), and the pores seem to be formed with many wrinkles from the curling of sheets [39]. The structures of IGGO, rGOA-0, and rGOA-1 are further analyzed by XRD. The relevant XRD patterns (Figure 3) exhibit an significant structural change after the hydrothermal reduction.