ABB PM665 3BDS005799R1｜Device Tensiometer｜

• It is increasingly and urgently obvious that the world needs to move toward green, renewable
  energy sources. Key in realizing this infrastructure are energy-conversion devices such as
  hydrogen fuel cells and water electrolyzers. As their name suggests, these devices allow energy to
  be converted from one form (a fuel) to another (electricity), and vice versa, enabling a distributed
  and modular energy network. 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 heterogeneous porous electrodes comprised of agglomerates of catalyst particles (typically
  platinum supported on carbon), ion-conducting polymer (ionomer), and void space. The
  microstructure of the CL, including the size of the agglomerates, the ionomer coverage,
  porosity/tortuosity, etc. controls the complex gas, liquid, ion, and electron transport networks and
  impacts the overall kinetic, ohmic, and mass-transport performance of these devices.
  Characterization efforts have spanned micro-, meso-, and macro-scale techniques to probe
  structure-property-performance relationships of the CL.

  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.