Green hydrogen generated via water electrolysis from renewable energy sources will play a major role in the sustainable energy systems of the future. Liquid organic hydrogen carriers (LOHC) have the potential to enable inexpensive hydrogen storage and transportation in the existing infrastructure for fossil fuels. Within this context, the isopropanol/acetone couple serves as a light-LOHC system for electricity generation in a direct isopropanol fuel cell (DIFC) without CO2 emissions. While the proof-of-concept studies have been promising, the best suitable configuration for the central part of the DIFC, the membrane electrode assembly (MEA), remains unclear. The primary aim of this thesis project was the first-time investigation and optimization of MEAs and operation conditions for DIFCs. By combining temperatures of up to 100 °C and pressures of up to 400 kPa absolute, the power density of the DIFC could be increased from 60 mW cm-2 to 254 mW cm-2 under air operation. By means of electrochemical crossover measurements, it was possible to show that composite Nafion membranes such as Nafion XL exhibit enhanced resistance against isopropanol crossover. Further studies focused on the impact of crucial electrode parameters such as catalyst loading, ionomer content, and carbon support on the performance of DIFCs. High anode PtRu loadings proved to provide more active sites for the reaction and thereby increased the fuel cell's total current and power output. The cathode Pt loading was found to have a minor influence on DIFC performance. Moreover, the employment of advanced high surface area carbon support revealed superior performance to standard Vulcan carbon support. The achieved power density of 259 mW cm- 2 represents the highest power density in the reported research literature for this fuel cell type so far and outperforms the vast majority of direct methanol fuel cell tests. Dynamic voltage scans even showed the possible theoretic potential of DIFCs (380 mW cm- 2) if the poisoning problem of the PtRu catalyst ...
Untersuchung von Membranelektrodeneinheiten für die Direkt-Isopropanol-Brennstoffzelle ; Investigation of Membrane Electrode Assemblies for Direct Isopropanol Fuel Cell
2022-01-01
Theses
Electronic Resource
English
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