New Process Is Promising for Hydrogen Fuel Cell Cars

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The process, given the name hydrothermolysis, uses a powdered chemical called ammonia borane, which has one of the highest hydrogen contents of all solid materials, said Arvind Varma, R. Games Slayter Distinguished Professor of Chemical Engineering and head of the School of Chemical Engineering.

"This is the first process to provide exceptionally high hydrogen yield values at near the fuel-cell operating temperatures without using a catalyst, making it promising for hydrogen-powered vehicles," he said. "We have a proof of concept."

The new process combines hydrolysis and thermolysis, two hydrogen-generating processes that are not practical by themselves for vehicle applications.

Research findings were presented June 15 during the International Symposium on Chemical Reaction Engineering in Philadelphia. The research also is detailed in a paper appearing online in the AIChE Journal, published by the American Institute of Chemical Engineers, and will be published in an upcoming issue of the journal.

Ammonia borane contains 19.6 percent hydrogen, a high weight percentage that means a relatively small quantity and volume of the material are needed to store large amounts of hydrogen, Varma said.

"The key is how to efficiently release the hydrogen from this compound, and that is what we have discovered," he said.

The paper was written by former Purdue doctoral student Moiz Diwan, now a senior research engineer at Abbott Laboratories in Chicago; Purdue postdoctoral researcher Hyun Tae Hwang; doctoral student Ahmad Al-Kukhun; and Varma. Purdue has filed a patent application on the technology.

In hydrolysis, water is combined with ammonia borane and the process requires a catalyst to generate hydrogen, while in thermolysis the material must be heated to more than 170 degrees Celsius, or more than 330 degrees Fahrenheit, to release sufficient quantities of hydrogen.

However, fuel cells that will be used in cars operate at about 85 degrees Celsius (185 degrees Fahrenheit). Hydrogen fuel cells generate electricity to run an electric motor.

The new process also promises to harness waste heat from fuel cells to operate the hydrogen generation reactor, Varma said.

New process is promising for hydrogen fuel cell cars