Army scientists and engineers recently made a groundbreaking discovery – an aluminum nanomaterial they designed produces high amounts of energy when it comes in contact with water, or with any liquid containing water.
During routine materials experimentation at the U.S. Army Research Laboratory, a team of researchers observed a bubbling reaction when adding water to a nano-galvanic aluminum-based powder. The team further investigated and found that water – two molecules of hydrogen and one of oxygen – splits apart when coming into contact with their unique aluminum nanomaterial. The reaction surprised the researchers, but they soon considered its potential implications for future power and energy applications.
"The hydrogen that is given off can be used as a fuel in a fuel cell," said Scott Grendahl, a materials engineer and team leader. "What we discovered is a mechanism for a rapid and spontaneous hydrolysis of water."
Scientists have known for a long time that hydrogen can be produced by adding a catalyst (a substance that increases a chemical reaction rate) to aluminum. But these methods take time, elevated temperature, added electricity, and/or toxic chemicals such as sodium hydroxide, potassium hydroxide or acid.
"In our case, it does not need a catalyst," said Dr. Anit Giri, a physicist with the lab's Weapons and Materials Research Directorate. "Also, it is very fast. For example, we have calculated that one kilogram of aluminum powder can produce 220 kilowatts of energy in just three minutes."
That metric doubles if you consider the amount of heat energy produced by the exothermic reaction. "That's a lot of power to run any electrical equipment," Giri said. "These rates are the fastest known without using catalysts such as an acid, base or elevated temperatures."
The team demonstrated with a small radio-controlled tank powered by the powder and water reaction. Moments after mixing the powder with a small amount of water, a bubbling reaction produced a great deal of hydrogen, which was then used to power the model around the laboratory.
"We just take our material, put it in the water and the water splits down into hydrogen and oxygen," Grendahl said. "There are other researchers who have been searching their whole lives and their optimized product takes many hours to achieve, say 50 percent efficiency," Grendahl said. "Ours does it to nearly 100 percent efficiency in less than three minutes."
Additionally, since the nanomaterial powder has the potential to be 3-D printed, researchers envision future air and ground robots that can feed off of their very structures and self-destruct after mission completion. Researchers said one possible application of the discovery that may help future soldiers is the potential to recharge mobile devices for recon teams.
"These teams are out for a short number of days, three to five days, and a lot of that depends not only on their food supplies, but on how long their supplies last in terms of their equipment and right now that stems from lithium batteries," Grendahl said. "If we can recharge those batteries, they can stay out longer."