Superkondenzatori pripravljeni od aktivnog ugljika dobivenog iz kokosove ljuske

master's thesis

• Title (english): Supercapacitors prepared from the coconut shell active carbon
• Author: Ines Pehar
• Mentor: Zoran Mandić (mentor)
• Committee member: Zoran Mandić (predsjednik povjerenstva)
• Committee member: Marijana Kraljić Roković (član povjerenstva)
• Committee member: Vladimir Dananić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2023-01-27, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

U današnjem svijetu gdje održivost korištenja energije postaje jedno od važnijih pitanja, sve više se skreće pozornost na korištenje obnovljivih izvora energije. Kako bi se što više iskoristio potencijal takvih izvora, ključno je usavršiti koncept skladištenja energije u spremnicima kao što su baterije, gorive ćelije i superkondenzatori. U ovom radu istražena je mogućnost korištenja različitih vrsta aktivnog ugljika kao materijala za izradu elektroda superkondendzatora. Ispitani su aktivni ugljik dobiven iz kokosove ljuske CS i Norit DLC SUPER 30 (OVIA INOVACIJE). Za oba materijala je dobivena raspodjela veličina čestica metodom dinamičkog raspršenja svjetlosti DLS, krivulje termičke stabilnosti termogravimetrijskom analizom te FTIR spektri. Od oba materijala su zatim izrađene elektrode te su sastavljena dva superkondenzatora i ispitani elektrokemijskim analitičkim metodama. Provedena je elektrokemijska impedancijska spektroskopija EIS u rasponu frekvencija od 10 mHz do 100 kHz i kao rezultat su dobiveni Nyquistovi prikazi. Zatim je provedena ciklička voltametrija u rasponu potencijala od 0 do 2 V brzinom promjene potencijala od 20 mV/s. Također je provedeno galvanostatsko punjenje/pražnjenje GCD u 30 ciklusa u dvo- i troelektrodnom sustavu pri struji od 20 mA, nakon čega su se ponovila mjerenja EIS i cikličke voltametrije da se zabilježe promjene u kapacitetima i otporima u sustavu. Iz Nyquistovih prikaza moglo se zaključiti da ponašanje kondenzatora nije idealno, a vidljiv je veći unutarnji otpor CS elektroda u odnosu na Norit, te je u oba slučaja došlo do porasta unutarnjeg otpora nakon provedenih 30 ciklusa punjenja i pražnjenja. Iz oblika cikličkog voltamograma dalo se zaključiti da CS pokazuje bolje kapacitivne karakteristike na osnovu gotovo konstantnih vrijednosti struje prije i poslije 30 ciklusa. Iz krivulja punjenja i pražnjenja izračunati su specifični kapaciteti te se također vidi veći pad kapaciteta i niže vrijednosti kod Norita u odnosu na CS. Također su izračunati unutarnji otpori na osnovi pada napona te su pokazali puno veće vrijednosti kod CS što se može objasniti lošijim kontaktom između aktivnog materijala i strujnog kolektora.

Abstract (english)

In today's world, where the sustainable use of energy use is becoming one of the most important issues, more and more attention is being drawn to the use of renewable energy sources. In order to make the most of their potential, it’s crucial to perfect the concept of energy storage in devices such as batteries, fuel cells and supercapacitors. In this paper, the possibility of using different types of activated carbons as materials for supercapacitor electrodes was investigated. Activated carbon obtained from coconut shell CS and Norit DLC SUPER 30 were the two materials tested. For both materials, the particle size distribution was obtained using the DLS dynamic light scattering method, the thermal stability curve was obtained using thermogravimetric analysis, as well as the FTIR spectra. Electrodes were made from different materials, then two supercapacitors were assembled and tested using electrochemical analytical methods. Electrochemical impedance spectroscopy, EIS was performed in the frequency range from 10 mHz to 100 kHz and as a result Nyquist plots were obtained. Cyclic voltammetry was performed in the potential range from 0 to 2 V with a potential change rate of 20 mV/s. A 30-cycle galvanostatic charge/discharge, GCD, was also performed in a two- and three-electrode system at a constant current of 20 mA, after which EIS and cyclic voltammetry measurements were repeated to record changes in system capacitances and resistances. From Nyquist plots it was concluded that the behavior of the capacitor is not ideal, the internal resistance of CS electrodes seemed higher compared to Norit, and in both cases the internal resistance increased after 30 charging and discharging cycles. From the shape of the cyclic voltammogram, it was concluded that CS shows better capacitive characteristics based on almost constant current values before and after 30 cycles. Specific capacities were calculated from the charge/discharge curves, with a bigger drop in capacity and lower values found for Norit compared to CS. Internal resistances were also calculated based on the voltage drop and showed much higher values for CS, which can be explained by poorer contact between the active material and the current collector.

• Keywords: superkondenzator; aktivni ugljik; elektrokemijska impedancijska spektroskopija; ciklička voltametrija; galvanostatsko punjenje/pražnjenje
• Keywords (english): supercapacitor; active carbon; electrochemical impedance spectroscopy; cyclic voltammetry; galvanostatic charge/discharge
• Language: croatian
• URN:NBN: urn:nbn:hr:149:200406
• Study programme: Title: Chemical Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka kemijskog inženjerstva (magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2023-02-15 11:00:49