Synthesis of Watermelon Seed Husk Based Activated Carbon Ablated by Laser for SC Electrode Material and Adsorption of Methylene Blue Dye

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Anas Draidi
Kareema Dababat
Manal Tuffaha
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Abstract The aim of this project was to recycle the watermelon seed husks waste into a beneficial product. Not only did we accomplish this goal, but also produce from it superior activated carbon material that was used in both the making of supercapacitor (SC) electrode and as a methylene blue (MB) adsorbent. In order to recycle the seed husks (RSH) into activated carbon (AC), RSH needed to first be pretreated then carbonized by pyrolysis (CC) followed by a chemical activation process; in which the surface area of the carbon increased tremendously (AC). Lastly, some of the activated sample was subjected to laser ablation (LAC) to increase the surface pores even more. FTIR test was then performed to investigate the modification on the porosity and surface area of the samples (RSH, CC, AC and LAC). The results revealed the success of the activation (AC) and laser ablation (LAC) processes due to a noticeable increase in the functional groups, such as OH. Through their use in two applications—as a SC electrode and as a MB adsorbent—two major samples, including AC, and LAC, were examined for their behavior, effectiveness, and applicability. The samples were used to prepare the SC electrodes, by placing them in the SC cell separated by a filter paper drenched in KOH then sealed shut. Lastly, 3 types of electrochemical characterization methods were run, such as: Cyclic voltammetry (CV), galvanostatic charging discharging (GCD) and electronic impedance spectroscopy (EIS). It was established from this that, generally speaking, utilizing low scan rates and current values delivers the best results since these values restrict the ions' ability to diffuse into electrode pores at higher values. With the highest specific capacitance values (190.61, 169.08, and 190.89 f g-1) at the lowest current and scan rate values, all tests (CV, GCD, and EIS, respectively) have shown that LAC was the best sample. Additionally, LAC obtained the lowest equivalent series resistance of 0.11 ohm and the lowest voltage drop value of 2.20 V from the GCD study. As for the MB adsorption, it was found that LAC was the best adsorbent, with an efficiency reaching 99.1% in just 40 minutes.