Investigation of catalyst structure and dispersion methodology on PEMFC catalytic inks and resulting electrodes
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Materials chemistry (MPMCN), MSc
Publicerad
2023
Författare
Ulberstad, Emma
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The demand for green energy increases every year, pushing the development of sus tainable energy sources. Proton exchange membrane fuel cells (PEMFCs) are a
promising technology for renewable energy conversion due to their clean emissions
and high energy-conversion efficiency. The electrodes are a core part of PEMFCs,
containing the catalyst at which the electrochemical reactions occur, where hydro gen and oxygen are converted to water and energy. To enhance cost efficiency,
performance and durability of PEMFCs, it is essential to better understand the
complex and partly unknown properties of the electrode and optimize the electrode
production process. There is a need to better understand the dispersion method of
the catalyst ink that makes up the electrode because it is one of the major factors
determining the electrode properties. The effect of catalyst ink materials, dispersion
technique and parameters on the catalyst ink microstructure were studied using rhe ological measurements and light microscope imaging of the electrodes. Dispersion by
ultrasonication at higher vibrational amplitude showed an increase in viscosity and
less visible agglomerates on the electrode surface as compared to lower amplitudes.
A continuous decrease in apparent agglomerate size and abundance was found with
increasing ultrasonic energy input. The results also showed a partly unexpected rhe ological trend where highly dispersed inks exhibit poorer rheological properties, such
as low viscosity and elastic modulus for the applied coating method as compared to
less dispersed inks. Ultrasonication and bead-milling dispersion method resulted in
inks with different rheological properties. The investigation showed that rheology
and microscopy are able to only partly capture the complex characteristics of the
agglomerated structures and complimenting techniques like e.g. SEM and DLS can
help further investigation. With this work, an optimization of the ink dispersion
process was achieved and further insight into the dispersion parameters allowed to
establish dispersion design rules, e.g. regarding the ultrasonic power and energy
input, and to further elucidate the interdependency between ink components and
dispersion methodology.
Beskrivning
Ämne/nyckelord
proton exchange membrane fuel cell, catalyst, rheology, catalyst layer.