| Popis: |
Diplomsko delo sestoji iz pregleda literature, v katerem so predstavljeni sodobni trendi in metode na področju elektrokatalitske redukcije CO2 z uporabo obnovljive električne energije kot alternativne strategije za zmanjšanje pomanjkanja električne energije in globalnega segrevanja. Redukcija molekule CO2 je kinetično počasen proces, zato je treba zasnovati energetsko učinkovit, selektiven in cenovno ugoden elektrokatalizator. Materiali na osnovi grafena so potencialno obetavni kandidati za pretvorbo CO2 zaradi svojih edinstvenih fizikalnih, mehanskih in elektronskih lastnosti. Poleg tega lahko njihovo površino modificiramo z različnimi strategijami, vključno z dopiranjem in tvorbo defektov. Zlasti dopiranje površine grafena s kovinskimi atomi ustvari edinstvena aktivna mesta za adsorpcijo in aktivacijo CO2. Poleg tega integracija grafena z drugimi atomi in molekulami omogoča sinergijski učinek, s čimer se poveča pretvorba CO2. V tem diplomskem delu so predstavljene osnove in nedavne študije o materialih na osnovi grafena za elektrokemijsko redukcijo CO2. Eksperimentalni del je bil izveden v skladu s teoretičnimi znanji za sintezo turbostratičnega grafena s tehniko bliskovnega Joulovega segrevanja (Flash Joule Heating). Namen teh poskusov je bil pridobiti turbostratični grafen s specifičnimi lastnostmi in primerjati uporabljene eksperimentalne parametre pri procesu bliskovnega Joulovega segrevanja s teoretičnimi. »Flash Joule Heating« (FJH) je napredna tehnika sinteze materialov, ki lahko skoraj vsako snov na osnovi ogljika pretvori v znatne količine turbostratičnega grafena, pri čemer se med pretvorbo ne uporabljajo topila ali reaktivni plini. To delo raziskuje morfologijo in lastnosti pridobljenega grafena. Ramanska spektoskopija sintetiziranega grafena pokaže, da je le ta sestavljen iz plasti turbostratičnega »flash« grafena (tFG), kjer je jasno opazno rotacijsko neskladje med sosednjimi plastmi v strukturi grafena, preostali del sintetiziranega grafena pa predstavljajo nagubane grafenske plošče. Prav tako pridobljeni Ramanski spektri in njihova analiza kaže na nizkointenziven ali odsoten pas D, kar potrdi turbostratično zlaganje grafena, ki se jasno razlikuje od turbostratičnega grafita. The bachelor’s thesis is comprised of a literature review, which describes the modern trends in the electrocatalytic CO2 reduction using renewable electricity as an alternative strategy for alleviating energy shortage and global warming issues. The CO2 reduction reaction is a kinetically sluggish process and for this purpose, an energy-efficient, highly selective and a low cost catalyst has to be designed. Graphene-based materials could be promising candidates for CO2 conversion because of their unique physical, mechanical, and electronic properties. In addition, the surface of graphene‐based materials can be modified by using different strategies, including doping, defect engineering and different wrapping shapes. By doping with metal atoms, it’s possible to create unique active sites on graphene for CO2 adsorption and activation. Besides, integration of graphene with other materials enables creation of a synergistic effect, thereby boosting CO2 conversion. In this bachelor’s thesis, the fundamentals of electrochemical CO2 reduction and recent studies on graphene‐based materials for CO2 reduction are summarized. The experimental studies were performed in accordance with the theoretical regimes for the synthesis of flash graphene via flash Joule heating technique. The purpose of these experiments was the obtaining of turbostratic flash graphene with given properties and the comparison of the experimental parameters of the electric explosion process with the theoretical ones. Flash Joule heating (FJH) is an advanced material synthesis technique, that can convert almost any carbon-based precursor into bulk quantities of graphene and uses no furnace and no solvents or reactive gases during the synthesis. This work explores the morphologies and properties of flash graphene (FG) generated from carbon black. It is shown that FG is partially comprised of sheets of turbostratic FG (tFG) that have a rotational mismatch between neighboring layers. The remainder of the FG is wrinkled graphene sheets that resemble non-graphitizing carbon. Raman spectroscopy analysis of the generated tFG shows a low-intensity or absent D band for FG and confirms the turbostratic stacking of FG, which is clearly distinguished from turbostratic graphite. |
