A new type of polymer electrolyte membrane (PEM) that’s being developed by researchers at the Department of Energy’s Sandia National Laboratories may bring the goal of a micro fuel cell closer to realisation.
Recently the membrane research team headed by Chris Cornelius demonstrated that the new (Sandia) PEA could operate as high as 140 degrees C and produce a peak power of 1.1 W per square centimeter and 2 A per square centimetre at 80 degrees C.
Under identical operating conditions, the SPEA material can deliver higher power outputs with methanol and hydrogen than Nafion, the current state-of-art PEM material for fuel cells. Because the SPEA material can operate at elevated temperatures, it provides several key benefits over Nafion. These include smaller fuel cell stacks because of better heat rejection, enhanced water management, and significant resistance to carbon monoxide poisoning.
Cornelius notes that a higher temperature PEM material is one of the goals of the Department of Energy’s (DOE) Hydrogen, Fuel Cells, and Infrastructure Technologies Program. By 2005, researchers hope to have developed polymer electrolyte membranes for automotive applications that operate at 120 degrees C for 2,000 hours with low membrane interfacial resistance.
A polymer electrolyte membrane is a critical component of a working fuel cell. Its function is to conduct protons efficiently and possess low fuel crossover properties. It must also be robust enough to be assembled into a fuel cell stack and have long life.
In developing the SPEA material, the team looked at the success and limitations of other PEM alternatives in order to develop a set of characteristics for their model material.
“At the beginning of this project we were considering several polymer families for a PEM alternative, including a family of polyphenylenes,” Cornelius says. “When the physical properties of one of the polyphenylenes being considered as a polymer electrolyte was improved and integrated into a working fuel cell, we happily discovered that it works extremely well compared to Nafion.”
Cornelius says that the SPEA material may be an enabling material that could have an impact on the fuel cell community and help Sandia become recognized as a fuel cell research organization.
“We have already completed initial material validation studies of our SPEA with the help of our battery group and Los Alamos National Laboratory,” he says.
The next steps, Cornelius says, are to reduce the internal resistance in the fuel cell membrane electrode assembly, optimise catalyst and ionomer composition, improve the properties of the SPEA material, conduct life cycle testing in a fuel cell environment, and assess the potential value for large-scale commercialisation of the polymer electrolyte.
Understanding the material’s capabilities and limitations are necessary steps in order to potentially improve the physical properties of SPEA material.
“We see this SPEA material as having the potential of being integrated into fuel cells ranging from microwatts to kilowatts,” he says. “Such a broad power range means that this Sandia Polymer Electrolyte aternative could be used in a fuel cell to power everything from sensors, cell phones, laptops, and automobiles.”