Chitins from Seafood Waste as Sustainable Porous Carbon Precursors for the Development of Eco-Friendly Supercapacitors

Abstract

Carbon materials derived from marine waste have been drawing attention for supercapacitor applications. In this work, chitins from squid and prawn marine wastes were used as carbon precursors for further application as electrodes for energy storage devices. Chitins were obtained through a deproteinization method based on enzymatic hydrolysis as an alternative to chemical hydrolysis as commonly presented in the literature. The obtained porous carbons were characterized using a BET surface area analyzer to determine the specific surface area and pore size, as well as scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), Raman spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), to characterize their morphology, composition, and structure. The electrochemical characterization was performed using a glassy carbon (GC) electrode modified with marine waste-based porous carbons as the working electrode through cyclic voltammetry and galvanostatic charge/discharge using ethaline, a choline chloride-based deep eutectic solvent (DES), as an eco-friendly and sustainable electrolyte. Squid and prawn chitin-based carbons presented a surface area of 149.3 m2 g−1 and 85.0 m2 g−1, pore volume of 0.053 cm3 g−1 and 0.029 cm3 g−1, and an associated specific capacitance of 20 and 15 F g−1 at 1 A g−1, respectively. Preliminary studies were performed to understand the effect of -OH groups on the chitin-based carbon surface with DES as an electrolyte, as well as the effect of aqueous electrolytes (1 mol L−1 sulphuric acid (H2SO4) and 1 mol L−1 potassium hydroxide (KOH)) on the capacitance and retention of the half-cell set up. It is provided, for the first time, the use of chitin-based carbon materials obtained through a one-step carbonization process combined with an eco-friendly DES electrolyte for potential application in energy storage devices.

Porous Carbon Materials Based on Blue Shark Waste for Application in High-Performance Energy Storage Devices

“…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 chondroitin sulfate-based carbon and the squid chitin-based carbon [12], which present a higher surface area and consequent lower capacitance. This may be due to the entirely different morphology of the materials.…”

“…With low intensity, the C-H bands of aliphatic hydrocarbons can be assigned to the band noted between 2900 and 2800 cm −1 in all three biocarbon samples [33,34]. The peak detected at around The spectra of raw blue shark chondroitin sulfate exhibit a clear and notable band between 3500 and 3250 cm −1 , which can be assigned to the stretching vibrations of the hydroxyl (-OH) groups [12]. However, this band is absent after the carbonization process.…”

“…The ATR-FTIR spectra of the blue shark and commercial chondroitin sulfate-based carbons, and the blue shark gelatine-based carbon (as well as their precursors) were studied in the range of 4000-600 cm −1 , and are presented in Figure 7. The spectra of raw blue shark chondroitin sulfate exhibit a clear and notable band between 3500 and 3250 cm −1 , which can be assigned to the stretching vibrations of the hydroxyl (-OH) groups [12]. However, this band is absent after the carbonization process.…”

“…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. Brandão et al [11,12,19] 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.…”

“…Several published papers used marine waste-based carbons for application as electrodes in energy storage devices, with promising results considering capacitance and retention over time. Brandão et al [11] recently presented glycogen (from mussel cooking wastewater) and chitin [12] (from squid pen and prawn exoskeleton) as precursors for producing carbons with a high porosity and specific surface area, up to 3.3 nm and 1526 m 2 g −1 , respectively. Glycogen-based carbon presented an associated specific capacitance of 657 F g −1 at a current density of 1 A g −1 , at 30 • C, with 99% retention after 1000 cycles.…”