Ion Exchange Materials with Enhanced Stability

Date created: 
Cation exchange membranes
Degradation mechanism
Anion exchange membranes
Fuel cells

Fuel cells are often seen as an alternative to batteries and internal combustion engines to provide electrical power in portable, stationary, or automotive applications. However, several challenges have to be overcome to enable widespread market penetration. One of these challenges is the limited lifetime of fuel cells, or more specifically, the durability and stability of polymer electrolyte membranes. In proton exchange membrane fuel cells, the chemical degradation of widely used perfluorosulfonic acid (PFSA) membranes can be inhibited by radical scavengers. Instead of time-consuming in situ investigations, radicals are widely generated ex situ by Fenton’s reagent, but this also leads to an unrealistic accumulation of iron species. In a newly developed, time saving test protocol, CeO2, ZrO2 and yttria-stabilized zirconia (YSZ) are investigated for their ability to protect PFSA membranes against radical attack and their diverse impact on the membrane properties. In alkaline anion exchange membrane fuel cells, the durability depends on the caustic resistance of the functional groups providing anion conductivity. Theoretical considerations are performed to understand the stability of benzimidazolium and imidazolium with different substituents for steric protection. Limited structural integrity of anion-conducting polymers in challenging environment can lead to restricted usability. The incorporation of crosslinks is investigated as a convenient approach to control ion exchange capacity, prevent dissolution and enhance anion conduction.

Document type: 
This thesis may be printed or downloaded for non-commercial research and scholarly purposes. Copyright remains with the author.
Steven Holdcroft
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.