## 3 Results
### Electrochemical Characterization
Figure 13: Galvanostatic charge–discharge curves in ethaline at 30 \({}^{\circ}\)C (1 st cycle) for gelatine and chondro-based sulfate-based carbons. Table 5 summarizes the electrochemical studies of the three materials studied in this work. For comparison, other fish waste-based carbons studied by this group were considered. The authors addressed different biopolymers recovered from marine waste sources as carbon precursors for application in energy storage devices. In this case, for the sake of comparison, the carbonization parameters (1000 \({}^{\circ}\)C for 1 h, under N\({}_{2}\) atmosphere) and the electrolyte conditions and setup during the electrochemical studies were kept constant. Within the literature, it is very difficult to find similar or identical carbonization protocols for biomass precursors for comparison, since the carbonization process leads to different characteristics in the obtained carbon materials. High-specific-area materials have a greater surface area per unit mass, allowing them to store and discharge more charge more effectively than low-specific-area materials. [PERSON] et al. (2011, 2012) showed that the higher the specific capacitance, the larger the surface area of carbons. An increased surface area can accommodate more electrolyte ions, leading to a more significant amount of stored charge. This statement is consistent with the results presented in Table 5, except with the blue shark chondro sulfate-based carbon and the squid chitin-based carbon ([PERSON] et al., 2011), which present a higher surface area and consequent lower capacitance. This may be due to the entirely different morphology of the materials. Numerous investigations have established a correlation between an augmented surface area and pore volume, which results in the availability of more active surface sites for charge accumulation ([PERSON] et al., 2011; [PERSON] et al., 2012; [PERSON] et al., 2013). Alongside its high specific surface area, the carbon derived from blue shark chondro sulfate also possesses a highly porous structure characterized by a substantial volume of pores. The porous structure in the biocarbon material contributes to its high specific capacitance. The pores create an additional surface area, allowing for more efficient charge storage. Moreover, the pores facilitate the movement of ions in and out of the electrode, enabling efficient ion diffusion. The capacity of electrolyte ions to penetrate and access the pores of biocarbon-based materials is a crucial factor that directly impacts the performance of these materials in energy storage devices. The easy accessibility of the pores to the electrolyte ions allows for effective charge transfer, leading to improved energy storage capabilities and overall device performance. Regarding capacitance retention, the blue shark precursors (chondroitin sulfate and gelatine) exhibited a value of 71% after 5000 cycles, while the commercial chondro sulfate precursor demonstrated a value of 86%. This may be evidence of the presence of more easily degradable residuals in the materials extracted from blue shark wastes. Figure 14 shows the Nyquist (Z\" vs. Z') plots for blue shark chondro sulfate, gelatine, and commercial chondro sulfate-based carbons coated on the GC electrode. The presented plots are associated with one fixed potential (0.5 V).