Document Type

Theses, Masters


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This thesis is about the research on alkaline fuel cell (AFC) technology to investigate the long term operation with air. The aim was to solve the two main problems arising from long term operation and especially from operation with air: • Dilution of the liquid electrolyte by the water from the reaction • Cell damage due to the formation of carbonate In recent years the development of fuel cells has gained a growing interest again. However the interest in alkaline fuel cells was low as the polymer electrolyte membrane fuel cell (PEMFC) seemed to be the superior system. One reason for this is this is the estimation that the AFC cannot be operated with air because of the reaction of CO2 and the electrolyte potassium hydroxide solution (KOH). This research project shows that it is possible to operate the AFC with air and hydrogen in place of pure oxygen and hydrogen. First of all tests were made with gas diffusion electrodes (GDEs) that are used to build the fuel cell. The electrodes were operated with air in a half cell. Even after thousand of hours in operation with unfiltered air no significant decrease of power was detectable. But testing electrodes in a half cell in only one part. The only way to get reliable results is to test the electrodes under real conditions; Long term operation in the alkaline fuel cell. For this purpose fuel cells were built with O2-electrodes that were manufactured according to the results of the half cell tests. In addition, many changes had to be done to develop the fuel cell and adopt it to the demands of the operation with air. The results are presented and discussed in this thesis. In the end it was possible to operate the AFC for several hundred hours with unfiltered air without damaging the cell. Proposals for future work are also given.


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