Researchers at Purdue University have discovered a new highly efficient technique for making hydrogen fuel cells for vehicles. Dubbed hydrothermolysis, the new process uses a high hydrogen-content powdered chemical called ammonia borane and combines two hydrogen generating processes — hydrolysis and thermolysis — to achieve conditions appropriate for use in vehicles. The technology has the potential to be twice as effective as current fuel cells at around half the temperature, and instead of requiring pressures of 5,000 psi like most hydrogen fuel cells today, this process requires a measly 200 psi.
“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. We have a proof of concept,” said Arvind Varma, R. Games Slayter Distinguished Professor of Chemical Engineering and head of the School of Chemical Engineering at Purdue. Currently hydrogen fuel cells run at a temperature of 85 degrees Celcius and require high pressures to function. Hydrolysis alone requires a catalyst to turn hydrogen into energy, and thermolysis requires a temperature of 170 degrees Celsius to function — separately they can’t be used in fuel cells. However, when you combine them and introduce ammonia borane into the reaction, the temperature lowers, the pressure requirements lower, and researchers believe that if scaled up this would be the perfect reaction to generate electricity for hydrogen fuel cell vehicles.
The new process generates hydrogen from 14 percent of the total weight of ammonia borane and water used in the system. “This is important because the U.S. Department of Energy has set a 2015 target of 5.5 weight percent hydrogen for hydrogen storage systems, meaning available hydrogen should be at least 5.5 percent of a system’s total weight,” he said. “If you’re only yielding, say, 7 percent hydrogen from the material, you’re not going to make this 5.5 percent requirement once you consider the combined weight of the entire system, which includes the reactor, tubing, the ammonia borane, water, valves and other required equipment.” The concept has been proved and the only missing link in the system is how to recycle the ammonia borane used in the reaction and return it to its original state so that it doesn’t create waste. Researchers believe that this system would be able to fuel vehicles as well as small appliances.
Via Science Daily