Analysis of the Microstructure Formation Process and Its Influence on the Performance of Polymer Electrolyte Fuel‐Cell Catalyst Layers

Abstract

To understand the formation process of the microstructure of the catalyst layer of a polymer electrolyte fuel cell (PEFC), we tried to observe the “real” structure of the catalyst ink by cryogenic scanning electron microscopy (cryo‐SEM). Catalyst inks with different water/alcohol compositions were successfully visualized, and they correlated well with the particle‐size distribution obtained by laser diffraction of the ink and the structures of the catalyst layers obtained by typical SEM. On the basis of other electrochemical characterization results, including current–voltage performance, oxygen reduction reaction kinetics, and mass‐transport properties, the microstructures of the catalyst inks and the catalyst layers were proposed. The proposed microstructures can explain the relationship between the catalyst materials and the performance of the cathode catalyst layer of the membrane electrode assembly through its formation and apparent properties. It was also found that the microstructure of the catalyst ink plays an important role in performance.

Preparation of PEMFC Electrodes from Milligram-Amounts of Catalyst Powder

“…[34][35][36][37] It is customary to carefully design the catalyst ink composition and coating parameters to accommodate each catalyst. However, because the purpose of this work is to encourage MEA testing at an earlier development stage, a standardized approach was taken.…”

“…While ECSA measurement only requires electron and proton access, good access to reactant O 2 is also required for ORR. Minor changes in the ionomer distribution in the electrode have been shown to significantly affect the ORR activity as well as fuel cell performance at high current density, 3,35,[37][38][39][40][41][42] a topic of great interest in the fuel cell community. 3,43,44 Therefore, it is not a surprise that these vastly diverse methods yield slightly different performance.…”

Hybrid approach combining multiple characterization techniques and simulations for microstructural analysis of proton exchange membrane fuel cell electrodes

“…4ccorrespond to ionomer aggregates while the thickness of ionomer film covering the support particles is observed to range from 5 to 12.5 nm. Agglomerates of ionomer, not forming thin films on the catalyst/carbon surface, have been found via cryogenic SEM of water-rich catalyst-ionomer inks[41].…”

Preparation procedure for the electrode slurries of polymer electrolyte fuel cells utilizing the irreversibility of ionomer adsorption onto Pt–C particles

“…27) Takahashi et al examined the relationship between the cell performance and microstructure of the freeze-dried slurry by varying the solvent type; however, the microscopic observation of the freeze-dried slurry by scanning electron microscopy (SEM) was unable to determine its macroscopic characteristics. 28) Among these works, several studies were devoted to the effect of the slurry parameters on the cell performance. Thus, Komoda et al examined the relationship between the particle dispersion in the slurry and cell properties.…”