Reduktion von Edelmetallen in der Wasserstoffelektrode bei der Polymerelektrolyt-Wasserelektrolyse
Jülich / Forschungszentrum Jülich GmbH, Zentralbibliothek, Verlag (2017, 2018) [Book, Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (VIII, 186 Seiten) : Illustrationen
In order to reduce CO2 emissions, the increased use of renewable energy sources is indispensable. The generation of electricity from renewable energy sources, however, is weather-dependent and intermittent. Chemical energy storage is considered a key technology for the utilization of irregularly generated electricity. Excess electricity can be converted into hydrogen by means of electrolysis of water. If required, a reconversion of the hydrogen can take place. Polymer electrolyte water electrolysis is capable of following the dynamic load profile of renewable energy sources, but large amounts of platinum are needed as a catalyst for the hydrogen production reaction. A main task is to reduce the amount of platinum used without affecting efficiency. Furthermore, the influence of reduced electrode loading on the long-term stability of the electrolyzer is largely unexplored. In this work, the influence of the reduction of the platinum content on the cathode of a polymer electrolyte water electrolyzer on its efficiency and long-term stability is investigated. On the one hand, the reduction of the loading is aimed at by the synthesis of novel, platinum-based catalysts with a high activity, and on the other hand a reduced amount of commercially available catalysts is used. These catalysts are subjected to physicochemical analyses and their electrochemical characteristics are recorded by means of half-cell measurements. For the study of cathode aging, protocols are being developed to simulate accelerated degradation of the cathode. In addition, the characteristics of these catalysts are recorded and analyzed under real electrolysis conditions before and after aging. By means of electron microscopy, the occurring aging mechanisms are examined more closely. A novel, microporous catalyst has been developed, which has a higher exchange current density than the reference material platinum. With the help of platinum-based commercially available catalysts, the loading was reduced by a factor of 80, with a slight deterioration in performance was found. While at a high cathode loading the accelerated aging did not change the cell characteristics, a small deterioration in cell efficiency was observed at a cathode loading of 0.01 mgPt cm−2. Electron microscopic examination of the aging mechanisms revealed platinum particle growth as a result of accelerated aging tests. Furthermore, a migration of the platinum particles was observed, the intensity of which depended on the applied overvoltage.