Konzept eines Selbstheilungsmechanismus für Polymerelektrolytmembranen

The fuel cell is attracting considerable interest as a potential future energy converter,
particularly in the automotive industry. It can be operated with high efficiency, emits no
pollutants and is independent of fossil fuels. The vision is that the fuel cell of the future
will not only be emission-free but will also develop its full potential in terms of sustainability. The fuel cell, which uses valuable materials in a complex production process,
should be durable. In accordance with the principles of the circular economy, a selfhealing mechanism for the polymer electrolyte membrane (PEM) is proposed in order
to extend the service life of the fuel cell many times over and thus conserve resources
and costs. The problem to be addressed is the currently unavoidable wear phenomenon, namely the formation of pinholes in the membranes of the fuel cell. These reduce
the overall performance during operation and lead to the premature end of the fuel cell's
life. Proton-conducting polymer membranes are particularly susceptible to pinholes,
which are installed in low-temperature fuel cells (60-80°C) in vehicle applications. This
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includes the polymer electrolyte membrane fuel cell (PEMFC), which is the state of the
art for commercial vehicle applications. Pinholes may occur during the production process or during operation. While the former can be avoided, the latter cannot currently
be prevented during operation. Frequent start-up cycles, in particular, lead to pinholes
during operation, as is the case in the automotive sector. This results in a continuous
reduction in the performance of the fuel cell, which ultimately leads to its end of life. This
motivates the investigation of self-healing mechanisms for pinholes in proton-conducting polymer membranes.
This dissertation presents a novel self-healing concept based on filler-forming enzymes
attached to the membrane. In the event of a pinhole formation, a monomer is introduced
externally and transported through the fuel cell until reaching the pinhole, where enzymes undergo polymerisation. The dissertation also presents the initial experimental
results and evaluates the feasibility of the self-healing concept, as well as the potential
for future research.