Sandia National Laboratories
researchers may have developed the key to making hydrogen cars a commercial
reality.
Sandia researcher Cy Fujimoto demonstrates his new flexible hydrocarbon polymer electrolyte membrane, which could be a key factor in realizing a hydrogen car. (Photo by Randy Montoya)
A major roadblock in the development of hydrogen cars has been the lack of
a reliable hydrogen fuel cell that works well in both dry and humid environments.
Hydrogen fuel cells are electrochemical engines that come in several different
varieties with the most common being the polymer electrolyte membrane (PEM)
fuel cell. PEM fuel cells use oxygen from the air and pressurized hydrogen to
create electricity, heat and water (steam) as byproducts. The electricity powers
the electric motor that turns the wheels of the car.
Sandia researcher Cy Fujimoto has developed a PEM using a different material
that appears to be as durable as current PEMs but which also operates well in
both dry and humid environments, unlike current PEMs.
“The findings have been quite intriguing and may impact the future of
hydrogen cars,” Fujimoto said.
In recent tests, the Sandia polymer outperformed current state-of-the-art fuel
cells in two categories. The new Sandia PEM material evolved from an earlier
generation Fujimoto and former Sandian Chris Cornelius developed five years
ago that operate at elevated temperatures.
The early Sandia fuel cell material, however, was not specifically designed
for automotive applications. Fujimoto is making adjustments so that it will
suit automakers’ needs, which include high proton conductivity at high
temperature and at low water content.
Fujimoto anticipates that the new materials he developed over the past year
and a half will make the Sandia PEM perform better at low relative humidity.
The chemistry allows him to control where and how much acid is deposited on
the polymer backbone, which enables fine-tuning of the size of the ion conducting
channels. With larger pathways for proton movement the membranes will work better
in low humidity environments.
Other acid-containing PEMS, such as Nafion, maintain a path for protons to
pass through when the membranes are hydrated. As they dehydrate, the path shrinks
and becomes disconnected, restricting proton movement. The result is diminished
function of fuel cells in dry desert climates like the Southwest.
Fujimoto compares the current state of PEMs to a path in a park.
“You can be moving right along and then come to a place where the path
breaks. A person walking the path can maneuver around the break and move on.
Not so with protons. They come to a dead end,” he says. “Automobile
manufacturers want a membrane that is reliable in all environments. They can’t
have one that functions well in a humid climate like Miami, for example, and
not work well in dry Albuquerque.”
Working through Sandia’s Intellectual Project Management, Alliances &
Licensing Department, Fujimoto is collaborating with a consortium of automobile
manufacturers to build the better PEM. He says a cooperative research and development
agreement (CRADA) and possible licensing of the technology are forthcoming.
Before the collaboration can proceed much further, he says, he needs to come
up with a way to “scale up the chemistry” so the membrane can be
mass-produced at a low cost.
“We have to get the cost of manufacturing the membrane below $25 per
square meter for the method to be practical for cars,” Fujimoto says.
“This is one of the biggest challenges yet.”