APPLICATIONS OF TECHNOLOGY:
- Fuel cells for aerospace, ground transportation, and consumer electronics
- Artificial photosynthesis
- Enhanced proton transport
- Increased ion exchange capacity
- Improved safety with block-copolymer electrolyte materials
Berkeley Lab researchers led by Nitash Balsara have developed a porous block-copolymer electrolyte membrane with enhanced capacity for proton transport when hydrated. Proton exchange membrane fuel cells (PEMFCs) have been used since the 1960’s in spacecraft and are extremely efficient converters of chemical energy into electricity. Semipermeable electrolyte membranes are key elements of these fuel cells designed to facilitate transport of ions while keeping oxygen and hydrogen gases separate to prevent an explosion. To develop a new generation of PEMFCs, the Berkeley Lab team fashioned a new membrane from block copolymers, a material similar to one used as a solid electrolyte in advanced lithium-ion batteries.
The team’s polymer electrolyte membrane (PEM) is made of a polystyrene-block-polyethylene-block-polystyrene (SES) copolymer. The proton transport efficiency of SES is limited, however, by the necessary swelling of the electrolyte material in the presence of water. Hydration is essential to the function of PEMs, as water causes the proton-conducting channels to form. The Berkeley Lab team overcame this problem with a technique that introduces nanopores into the block copolymer, accommodating the swelling. Tests indicate that pores comprising 5%-20% of electrolyte volume can increase proton transport 25% compared to membranes containing no pores. When the pore percentage increases beyond that amount, the membrane’s ion exchange capacity rapidly falls.
This same nanoporous block-copolymer may also be suitable for use in photoelectrochemical cells. Such devices may be employed in artificial photosynthesis systems, which work like fuel cells in reverse: Sunlight is used to split water into hydrogen and oxygen, gases that must be separated by a membrane to avoid recombination.
DEVELOPMENT STAGE: Proven principle
STATUS: Patent pending. Available for licensing or collaborative research.
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REFERENCE NUMBER: IB-2013-081