Title: Modification of mixed conducting oxide surfaces with platinum nanoparticles and its effect on electrochemical properties
Language: English
Authors: Riedl, Christoph 
Qualification level: Diploma
Keywords: solid oxide fuel cells; composite electrode; oxygen reduction
Advisor: Fleig, Jürgen  
Assisting Advisor: Schmid, Alexander 
Issue Date: 2019
Number of Pages: 69
Qualification level: Diploma
Preventing climate change, increasing sustainability of human life and lowering carbon dioxide emission are among of the biggest challenges of the 21st century. Therefore, research and development of new possibilities to produce electrical energy has high priority. Solid oxide fuel cells (SOFCs) are able to produce electricity directly from oxidizing fuels. They show high efficiency and are promising candidates for future energy supply. One of the main goals in SOFC research is lowering the operation temperature to intermediate temperatures (400 - 600 C). In the search of high performance intermediate temperature SOFCs, improving the kinetics of oxygen reduction on mixed ionic electronic conducting (MIEC) oxide surfaces is of great interest. Previous studies on La0.6Sr0.4FeO3 revealed much higher electrochemical activity in fuel gas after cathodic polarization and subsequent exsolution of iron(0) particles on the surface. In the course of the thesis, the effect of surface decoration at MIEC electrodes with platinum nanoparticles was studied. Symmetrical thin film samples of Gd0.1Ce0.9O2 (GDC10), SrTi0.7Fe0.3O3 (STF73) and La0.6Sr0.4FeO3 (LSF64) were prepared by pulsed laser deposition on yttria-stabilized zirconia single crystals and characterized before and after platinum deposition at 600 C by electrochemical impedance spectroscopy. Platinum nanoparticles were deposited on the MIEC surface by sputter deposition. The morphology of the platinum nanoparticles was studied using scanning electron microscopy (SEM) and the deposited amount of platinum was determined by inductively coupled plasma - mass spectrometry (ICP-MS). In humidified H2 platinum decoration led to improved ASR e.g. from 6 cm2 to 1 cm2 for STF73 at 600 C. In oxidizing atmospheres up to two orders of magnitude lower polarization resistance could be obtained by Pt decoration. Surprisingly, oxygen incorporation on surface decorated samples shows faster kinetics in lower oxygen partial pressure contrary to undecorated samples. This indicates that nanoparticle decoration changes the rate-limiting step for oxygen incorporation. Furthermore, the deposited amount of platinum was varied and the dependency of the ASR on the deposited platinum amount was investigated.
URI: https://resolver.obvsg.at/urn:nbn:at:at-ubtuw:1-128435
Library ID: AC15455654
Organisation: E164 - Institut für Chemische Technologien und Analytik 
Publication Type: Thesis
Appears in Collections:Thesis

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