ABB PFSK113 7625013-S  DCS Signal transmission unit module

The efficiency and cost of these devices have vastly improved over

the last few decades, but those gains (in particular for fuel cells) have stagnated in recent years due
to performance limitations and high costs associated with their catalyst layers (CLs). This
dissertation focuses on fuel-cell CLs, although the fundamental principles and insights gained are
applicable to electrolyzers and other energy-conversion devices that rely on similar CL paradigms
and architectures.

CLs are made from precursor CL inks, which are colloidal dispersions of the ionomer and catalyst
particles, dispersed in solvent. CL studies are complicated by the multiple material types used
(varying ionomer chemistry, catalyst loading, carbon support type, solvents) and disparate ink
deposition and drying methods that render no two CLs alike; this makes it difficult to compare
across these different studies. Additionally, within the community, CL fabrication has traditionally
been treated as a black art, and the details of the fabrication process (ink composition, casting
method, etc.) are typically inconsistently reported, because emphasis has been placed on
understanding CL properties and performance and not the forces controlling that formation
process. However, it is increasingly clear that simply being able to characterize CLs is not enough.

To enable predictive control and rational design of CLs, it is vital to understand how and why (in
addition to what) specific microstructures form.

This dissertation sets out to uncover systematically the underlying fundamental interactions
between the ink components in solution, which ultimately govern CL microstructure (agglomerate
structures and sizes, ionomer coverages, etc.) and performance once cast. We begin by introducing
all relevant parameters in the CL ink fabrication process and conducting a literature-based
parameter screening to test correlation between ink variables and performance metrics. The
analysis reveals that while no single parameter is controlling, solvent identity and ionomer-tocatalyst-particle ratio correlate well with performance metrics. This suggests ionomer/solvent,
ionomer/particle, and ionomer/solvent/particle interactions merit further investigation.