Highly conductive Proton Exchange Membrane (PEM)

Proton Exchange Membranes (PEMs) are used in a wide range of applications, including PEM fuel cells (PEM-FCs) and ion exchange processes in water and other purification processes. PEMs are used in commercial water electrolysis systems and similar applications. The high price of perfluorinated Nafion® membranes (the current standard for various PEM applications) and the environmental hazards associated with their disposal have prompted research into the possibility of a low-cost, non-perfluorinated alternative. The development of novel membranes that are cheap to manufacture and possess high ion conductivity, and selectivity combined with mechanical and chemical strength, has long been a goal for polymer chemists. Various PEMs have been studied, including sulfonated Polyarylene Ether Ether Ketone (sPEEK), sulfonated polyarylene ether sulfone (PSU), Polyvinylidene Difluoride (PVDF)-graftstyrene, acid-doped polybenzimidazole and polyphosphazene. However, the membranes prepared from sPEEK, polyphosphazene and PSU possess low proton conductivity. More rigorous sulfonation of these membranes results in better proton conductivity, but the polymers then become water-soluble. Impregnation of polybenzimidazole with low-molecular-weight acids, for example, does result in high proton mobility, but these acids will leach out of the membrane over time. The environmental hazards of disposing of PVDF polymers are significant, and an efficient, cheap membrane that can last at least several thousand hours in a PEMFC is required. Currently, only the perfluorinated polymer Nafion is suitable for this application.

Project
In this project, a highly conductive proton exchange membrane was prepared via a novel, simple methodology. The project was divided into a number of working elements
Synthetic Chemistry
> Preparation of experimental set-up
> Extensive experiments with chemical reaction conditions
> Result: proof of principle of chemistry with defined parameters
Functional membrane synthesis
> Optimization of the reaction parameters of polymerization using selected components
> Result: optimized membrane syntheses with several possibilities
Follow-up treatment methodology
> Variation of several follow-up treatment strategies (thermal/chemical)
> Optimization follow-up treatment procedures > Result: control over several mechanical and chemical properties of the membranes
Testing
> Testing of all individual steps and methodologies
> Testing of the functional membrane for the essential properties

Benefits
The synthesis of this membrane could mean a major step forward in the production of DMPEMFCs. The present problems with water management and methanol permeation by the membrane can be solved by the use of this very cost-effective membrane.

Project coordinator
> KEMA, the Netherlands

Project details
> EOS-LT, NEO
> Duration: July 2008 – June 2010