New alkaline membrane for cheaper fuel cells
A NEW type of fuel cell membrane made from quaternary phosphonium–based polymers could allow for the production of cheaper fuel cells which do not require the use of expensive precious metal catalysts.
Yushan Yan, chemical and environmental engineering professor at the University of California, Riverside, and his team developed the alkaline membrane, which contains the polymeric ionomer TPQPOH with a tris(2,4,6-trimethoxyphenyl)phosphonium unit. TPQPOH is very soluble in low-temperature water-soluble solvents, and has high ionic conductivity and alkaline stability. The membrane works on the basis of hydroxide ion exchange rather than hydrogen ion exchange.
In a basic environment, created by the hydroxide ions, the over-potential of cathode oxygen reduction can be significantly reduced, which increases the efficiency. It is also possible to use a wide range of fuels including hydrogen, methanol, ethanol, and ethylene glycol.
Fuel cells containing the alkaline membrane have already been shown to be durable and have high energy and power density. Yan achieved a power density of 250 mW/cm2 with the membrane. Non-precious metals such as iron, cobalt, nickel and silver can be used as catalysts, rather than palladium or platinum, the latter of which topped $2000 an ounce (28.3g) in 2009.
“This is a breakthrough that will make fuel cells so efficient and inexpensive that it will revolutionize energy conversion and storage on a global scale.” says Yan. He believes the new membrane could replace the commonly-used Nafion membrane.
The research was published in Angewandte Chemie (doi: 10.1002/anie.200806299), and the technology has been licensed by Full Cycle Energy, a Californian start-up company.
