haku: @instructor Kallio, Tanja / yhteensä: 25
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| Tekijä: | Sorsa, Olli |
| Työn nimi: | PtCo-katalyytti polttokennon hapenpelkistysreaktiossa |
| PtCo catalyst for oxygen reduction reaction in fuel cell | |
| Julkaisutyyppi: | Diplomityö |
| Julkaisuvuosi: | 2015 |
| Sivut: | vii + 60 Kieli: fin |
| Koulu/Laitos/Osasto: | Kemian tekniikan korkeakoulu |
| Oppiaine: | Kemia (KE3001) |
| Valvoja: | Murtomäki, Lasse |
| Ohjaaja: | Kallio, Tanja |
| Elektroninen julkaisu: | http://urn.fi/URN:NBN:fi:aalto-201510164728 |
| Sijainti: | P1 Ark Aalto 3133 | Arkisto |
| Avainsanat: | fuel cell oxygen reduction reaction electrocatalysis electrodeposition polttokenno hapenpelkistysreaktio elektrokatalyysi sähkösaostus |
| Tiivistelmä (eng): | A fuel cell is an electrochemical device which transfers the chemical energy of a fuel (often hydrogen) into electricity with higher efficiency than a combustion engine. This happens through electrochemical reactions so that fuel is oxidized at an anode and oxygen is reduced at a cathode. Oxygen reduction is one of the major cell performance determining factors. As an oxygen reduction reaction catalyst, carbon supported platinum nanoparticles are most commonly used. Due to the high cost of platinum and its moderately low durability alternative catalysts are being researched. One of these alternatives is a platinum alloy catalyst in which a low cost transition metal is alloyed with platinum. In this work cobalt has been selected as the transition metal due to mainly three reasons. Firstly, it forms a stable Pt3Co face centred cubic structure in which platinum atoms are closer to each other and therefore more active for oxygen reduction. Secondly, as a less noble metal cobalt dissolves more easily than platinum and therefore increases its durability. Finally, cobalt also catalyses oxygen reduction. In the literature part applications of fuel cells, theory of oxygen reduction, synthesis methods of alloy catalysts and characterizing methods of a fuel cell catalyst are reviewed. The goal of this work is to develop a practical method to synthesize alloy catalysts and to find out whether cobalt increases the oxygen reduction activity of platinum or its durability in fuel cell conditions. In the experimental part PtCo catalyst has been synthesized using two methods: reduction through microemulsion to form nanoparticles and by electrodeposition from a liquid crystal phase. The electrodeposition generates mesoporous particles that have a diameter of 1-3 μm. These catalysts were compared to a commercial platinum nanoparticle catalyst and to platinum catalysts prepared using the same methods. All catalysts were examined in a fuel cell and additionally nanoparticle catalysts were studied using a rotating disc electrode. The nanoparticles were also characterized using a thermo gravimeter, a transmission electron microscope and an X-ray diffractometer and the mesoporous microparticles were characterized using a scanning electron microscope and an X-ray fluorescence spectrometer. The alloy nanoparticles were prepared using three different atomic ratios: Pt3Co, PtCo and PtCo3. Pt3Co is the most studied in literature and was found to be the best ratio. The electrodeposited catalysts proved to be significantly more active towards oxygen reduction than the nanoparticles. Especially using a co-deposited PtCo-catalyst 50 % higher maximum power was achieved when compared to the commercial catalyst. Additionally, the electrochemical characterization suggests that cobalt truly improves the durability of platinum. |
| ED: | 2015-11-08 |
INSSI tietueen numero: 52335
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