Student: Lavková Jaroslava
Školitel: Doc. Mgr. Iva Matolínová, Dr.
Stav práce: obhájená
Abstrakt:
Proton exchange membrane fuel cells (PEMFC) are expected to be future power production system for clean and efficient generation of electricity from hydrogen and hydrocarbons. Platinum in pure form or alloyed with other elements is regarded as the only choice so far for high and stable performance. As a consequence fabrication of fuel cells would be expensive and wide production impossible. For this reason substantial decrease of Pt loading and research of new low cost anode materials with high activity is necessary. Pt - cerium oxide systems have been reported to be significantly active catalysts for CO oxidation, hydrogen production, oxidation of ethanol and decomposition of methanol.
Realization of planar on-chip micro fuel cells and on-chip micro reactors requires use of new types of thin film catalysts made by physical deposition techniques. The characterization of these thin films, the control of their elaboration and the optimization of the properties of such catalysts represent main goals of the µ-FC development. Challenging aspect of this concept is that thin porous film catalysts should meet the same requirements as powders – high activity and large specific surface.
In the Prague laboratory, morphology of the catalytic films, namely thickness, roughness and porosity will be investigated by Scanning Electron Microscopy (SEM). Cross-sectional observation will be done by preparing thin lamellas using a dual beam microscope - Focus Ion Beam (FIB) and SEM equipped with nanomanipulators and Gas Injection System (GIS). Due to high sensitivity of investigated metal-oxide thin films to sputtering, the best parameters of lamella covering and thinning will be investigated.
In the Dijon Laboratory, the catalyst film lamellas will be investigated by transmission electron microscopy. The high resolution mode allows to localize precisely (at atomic scale) and to analyze the nano-objets. In addition to EDX (Energy Dispersive X-ray spectroscopy), Electron Energy Loss Spectroscopy (EELS) and Energy Filter TEM (EFTEM) techniques will be used to obtain informations on the chemical state of the atoms. These signals can be obtained simultaneously, allowing direct correlation of image and chemical data with nanometer precision.
These different techniques will help to optimize the elaboration of porous thin films and to control the properties of very specific nano-objects like Pt-CeO2 of high interest in fuel cell applications. Understanding the mechanisms of catalytic processes will be one of the most important targets of the project because it would permit more efficient development of new systems.