Sinteza grafenova oksida i reduciranoga grafenova oksida te njihova površinska modifikacija za primjenu u superkondenzatorima

doctoral thesis

• Title (english): Graphene oxide and reduced graphene oxide synthesis and their surface modification for supercapacitor application
• Author: Denis Sačer
• Mentor: Marijana Kraljić Roković (mentor)
• Committee member: Zoran Mandić (predsjednik povjerenstva)
• Committee member: Elvira Vidović (član povjerenstva)
• Committee member: Sanjin Gutić https://orcid.org/0000-0002-5780-8022 (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2018-12-10, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Basic Technical Sciences; Materials
• Universal decimal classification (UDC): 66 - Chemical technology. Chemical and related industries

Abstract

Grafen je sloj ugljika debljine jednog atoma koji posjeduje delokalizirane π elektrone te dobru električnu provodnost što mu, uz veliku specifičnu površinu, otvara mogućnost primjene u elektrokemijskim pretvornicima i spremnicima energija. Fizikalna i kemijska svojstva grafena kao i njegove dimenzije ovise o načinu sinteze. U ovom radu grafen je sintetiziran kemijskim putem koristeći različite forme grafita kao prekursor. Prvi stupanj sinteze se odnosio na dobivanje grafenova oksida (GO) iz kojeg se redukcijom dobiva reducirani grafenov oksid (rGO). Redukcija GO predstavlja vrlo važan korak samog procesa u kojem je neophodno ukloniti niz različitih kisikovih funkcijskih skupina vezanih na grafensku strukturu. Poželjno je provesti redukciju u što većem iskorištenju te osigurati uvjete kod kojih će se spriječiti aglomeracija grafena u grafit. U ovom radu detaljno je proučavan utjecaj konačnog stupnja redukcije na kapacitivna svojstva dobivenog rGO. Također je istraživana mogućnost korištenja ekstrakta lista masline (ELM) i kositrova (II) klorida kao ekološki prihvatljivih reducensa. Strukturne i morfološke karakteristike materijala određene su korištenjem Ramanove spektroskopije, rendgenske fotoelektronske spektroskopije (XPS), rendgenske difrakcijske analize (XRD), infracrvene spektroskopije s Fourierovim transformacijama signala (FTIR), termogravimetrijske analize (TGA) i skenirajuće elektronske mikroskopije (SEM). Iz dobivenih materijala priređeni su superkondenzatori koji su testirani metodom cikličke voltametrije i metodom elektrokemijske impedancijske spektroskopije (EIS). Stabilnost superkondenzatora testirana je punjenjem/pražnjenjem superkondenzatora tijekom 1000 ciklusa kod konstantne struje. Svi priređeni materijali pokazali su dobra kapacitivna svojstva u otopini 0,5 mol dm^-3 Na2SO4. U svrhu poboljšanja kapacitivnih svojstava, GO je modificiran molekulama anilina i o-fenilendiamina. Detaljno su istraženi uvjeti modifikacije te su određena fizikalno-kemijska svojstva dobivenih materijala.

Abstract (english)

Graphene is a monolayer of carbon atoms which possesses delocalized π electrons and a good electrical conductivity. Good electrical conductivity with a large specific surface area opens up the possibility of its application in electrochemical energy storage devices. Physical and chemical properties of graphene as well as its sheet size depend on the synthesis method. In this paper, graphene was chemically synthesized using various graphite forms as precursors. In the first step graphene oxide (GO) was obtained and it was used for further synthesis of reduced graphene oxide (rGO). The reduction of graphene oxide is a crucial step in which it is necessary to remove a variety of oxygen functional groups bonded to the graphene structure. It is desirable to achieve a high degree of reduction and to ensure electron conductivity with preventing the graphene agglomeration. In this paper the influence of the degree of reduction on the capacitive properties of the obtained rGO was studied in details. Additionaly, the possibility of using olive leaf extract (ELM) and tin (II) chloride as ecologically acceptable reducing agents was studied. Structural and morphological characteristics of the obtained materials were determined by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD), Fouirer-transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). By using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) methods it was shown that the all prepared materials exibited good capacitive properties in 0,5 mol dm^-3 Na2SO4 solution. The prepared materials were used to asemble supercapacitors that were tested by cyclic voltammetry and EIS methods. The stability of the supercapacitors was determined by charging/discharging at constant current during 1000 cycles. In order to improve its capacitive properties, GO is modified by the two different aromatic amines: aniline and o-phenylenediamine. They can contribute to the pseudo-capacitive effects and increase the overall capacitance of the base materials. Modification conditions and physicochemical properties of the obtained materials were studied in details.

• Keywords: grafenov oksid; reducirani grafenov oksid; modificirani grafenov oksid; ekstrakt lista masline; superkondenzatori; SnO2
• Keywords (english): graphene oxide; reduced graphene oxide; modified graphene oxide; olive leaf extract; supercapacitors; SnO2
• Language: croatian
• URN:NBN: urn:nbn:hr:149:590628
• Promotion: 2018
• Project: Number: IP-2013-11-8825; Title: Elektrokemijski superkondenzator visoke snage i velikog sadržaja energije za primjenu u električnim vozilima; Title: High power-high energy electrochemical supercapacitor for hybrid electric vehicles; Acronym: ESUP-CAP; Leader: Zoran Mandić; Jurisdiction: Croatia; Funder: HRZZ; Funding stream: IP
• Study programme: Title: Chemical Engineering and Applied Chemistry - Doctoral course; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje tehničkih znanosti, polje kemijsko inženjerstvo (doktor/doktorica znanosti, područje tehničkih znanosti, polje kemijsko inženjerstvo)
• Type of resource: Text
• Extent: 201, IV str. ; 30 cm
• File origin: Born digital
• Access conditions: Open access
• Created on: 2023-08-29 08:19:38