Record-breaking Hydrogen Storage Materials For Use In Fuel Cells Developed

Scientists at the University of Virginia have discovered a new class of hydrogen storage materials that could make the storage and transportation of energy much more efficient — and affordable — through higher-performing hydrogen fuel cells.

“In terms of hydrogen absorption, these materials could prove a world record,” Adam B. Phillips of the University of Virginia said. “Most materials today absorb only 7 to 8 percent of hydrogen by weight, and only at cryogenic [extremely low] temperatures. Our materials absorb hydrogen up to 14 percent by weight at room temperature. By absorbing twice as much hydrogen, the new materials could help make the dream of a hydrogen economy come true.”

In the quest for alternative fuels, U.Va.’s new materials potentially could provide a highly affordable solution to energy storage and transportation problems with a wide variety of applications. They absorb a much higher percentage of hydrogen than predecessor materials while exhibiting faster kinetics at room temperature and much lower pressures, and are inexpensive and simple to produce.

“These materials are the next generation in hydrogen fuel storage materials, unlike any others we have seen before,” Shivaram said. “They have passed every litmus test that we have performed, and we believe they have the potential to have a large impact.”

The inventors believe the novel materials will translate to the marketplace and are working with the U.Va. Patent Foundation to patent their discovery.

“The U.Va. Patent Foundation is very excited to be working with a material that one day may be used by millions in everyday life,” said Chris Harris, senior licensing manager for the U.Va. Patent Foundation. “Dr. Phillips and Dr. Shivaram have made an incredible breakthrough in the area of hydrogen absorption.”

Bellave S. Shivaram and Adam B. Phillips, the U.Va. physicists who invented the new materials, will present their finding at 8 p.m., Monday, Nov. 12, at the International Symposium on Materials Issues in a Hydrogen Economy at the Omni Hotel in Richmond, Va.

Phillips’s and Shivaram’s research was supported by the National Science Foundation and the U.S. Department of Energy.

Improved Ion Mobility Is Key To New Hydrogen Storage Compound

 A materials scientist at the National Institute of Standards and Technology (NIST) has deciphered the structure of a new class of materials that can store relatively large quantities of hydrogen within its crystal structure for later release. The new analysis may point to a practical hydrogen storage material for automobile fuel cells and similar applications.

The abundant element hydrogen could play a role in replacing carbon-based fuels for transportation in the future, but researchers first must develop a method to store and release large amounts of the highly flammable, odorless invisible gas economically and safely. There are materials that are known to trap relatively large quantities of hydrogen, at normal pressures, but to date they all require heating to fairly high temperatures to release the hydrogen.

Hui Wu, a research associate from the University of Maryland working in a cooperative research program at the NIST Center for Neutron Research, has been investigating a new hydrogen storage compound that mixes lithium amide with lightweight metal hydrides. Lithium amide can hold more than 10 percent of hydrogen by weight, well above the 6 percent target set by the U.S. Department of Energy as a 2010 goal for a hydrogen storage material for transportation. The material absorbs and releases hydrogen reversibly, but both absorbing and releasing the hydrogen requires high temperatures and also produces a toxic byproduct, ammonia.

Metal hydrides also store hydrogen, though not as well, but recently it's been shown that a combination of the two not only can store significant quantifies of hydrogen but also can release it at lower temperatures than the lithium amide alone (about 100 degrees Celsius) while generating much less ammonia.

To understand how the compound achieves this, Wu used neutron analysis to work out the atomic structure of the material, which she found consists of layers of calcium between which lithium ions travel rapidly. The easy travel allows the material to transfer the hydrogen at lower temperatures. Also the hydrogen ions in the amide and hydride mixture combine easily and release hydrogen at lower temperature without creating much ammonia.

"I found that the mobility of small ions in the mixed amide-hydride system greatly improves hydrogen storage properties," Wu explains. "This finding helps us understand how hydrogen travels in and out of these systems and that may lead to a rational development of better materials for hydrogen storage."

 Journal reference:

1. H. Wu. Structure of ternary imide Li2Ca(NH)2 and hydrogen storage mechanisms in amide-hydride system. Journal of the American Chemical Society ASAP Article, Web release date: April 30, 2008. 

 2. Adapted from materials provided by Technical University Of Denmark.