DEVELOPMENT OF SUPERCAPACITOR CATHODE BASED ON NICKEL METAL ORGANIC FRAMEWORK (NI-MOF) AND CARBON NANOTUBE (CNT) COMPOSITE USING SOLVOTHERMAL METHOD

• Main Author: Firdaus, Idam
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86775
• Institution: Institut Teknologi Bandung

Supercapacitors are energy storage devices with high energy and power density. They store energy through an electrostatic double-layer mechanism and pseudocapacitance reactions, enabling rapid energy storage and release without efficiency loss even after numerous cycles. Electrode materials, such as nickel, play a critical role in the electrochemical performance of these energy storage devices. Nickel-based Metal-Organic Frameworks (Ni-MOF) have gained attention due to their high theoretical capacitance, availability, ease of synthesis, and chemical stability. However, despite these advantages, challenges such as inadequate rate capability and limited cycling properties remain obstacles to wider applications. Therefore, to achieve optimal Ni-MOF-based electrode materials, the addition of a capping agent such as Multi-Walled Carbon Nanotubes (MWCNTs) is required. MWCNTs possess a high specific surface area, excellent electrical conductivity, unique hollow structures, and stable chemical properties, which contribute to enhancing electrical conductivity. In this study, Ni-MOF(BDC) material with variations of 1 ml and 5 ml of ethylene glycol was successfully synthesized using the solvothermal method at 150°C for 48 hours, followed by drying overnight at 60°C. The material's characteristics were analyzed using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, and Brunauer-Emmett-Teller (BET) analysis to confirm the structure and morphology of the material. The electrochemical performance of the Ni-MOF(BDC)-based supercapacitor was tested using Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS) with 2M KOH as the electrolyte solution. The characterization results revealed that the Ni-MOF(BDC) material is a nanosheet-like material with an average crystal size of 7.82 nm. The addition of ethylene glycol, which acts as a capping agent, influenced the material's morphology by thinning the sheet-like structure, reducing its thickness from 0.13 µm to 0.07 µm (a decrease of 0.06 µm). Furthermore, the Ni-MOF(BDC) material with the addition of 5 ml of ethylene glycol exhibited a larger surface area (9.5197 m²/g) compared to the material with 1 ml of ethylene glycol (9.3291 m²/g). Regarding the electrochemical testing results, the Ni-MOF(BDC) material with the addition of 5 ml of ethylene glycol demonstrated a higher specific capacitance value (281.65 F/g) compared to the material with 1 ml of ethylene glycol. Based on the synthesis results, characterization testing, and electrochemical performance evaluation of the two materials, the most optimal material was identified as Ni-MOF(BDC) with the addition of 5 ml of ethylene glycol. Further research was conducted by varying the addition of the capping agent MWCNT at concentrations of 1%wt, 3%wt, and 5%wt. The addition of 1%wt MWCNT reduced the crystal size to 6.68 nm and increased the surface area to 20.178 m²/g. Using the Barrett-Joyner-Halenda (BJH) method during the adsorption process, the main peak indicating the dominant pore diameter was found to be above 2 nm, categorizing the Ni-MOF(BDC)/1%CNT material as mesoporous. Moreover, the addition of 1%wt MWCNT also improved electrochemical performance, including achieving an optimal reduction current of 17.17 mA and oxidation current of 36.31 mA, increasing the specific capacitance to 495.21 F/g. According to the Nyquist Plot, the Ni-MOF(BDC) material with the addition of 1%wt MWCNT exhibited the smallest semicircular diameter. This reduction indicates that MWCNT effectively lowered the charge transfer resistance. Consequently, this facilitated an increased electron transfer rate, ultimately enhancing overall electrochemical performance. From this study, it can be concluded that Ni-MOF(BDC) material with the addition of 5 ml of ethylene glycol and 1%wt MWCNT is the most optimal material for application as a supercapacitor electrode. Keywords: energy storage, supercapacitor, nickel metal-organic framework, carbon nanotube, solvothermal. ?