Improved Ion Mobility Is Key to New Hydrogen Storage Compound

May 14, 2008
Improved Ion Mobility Is Key to New Hydrogen Storage Compound
The atomic structure of the mix of lithium amide with lightweight metal hydrides shows layers of calcium that the lithium ions can sprint through. This facilitates hydrogen storage and release. Credit: NIST

A materials scientist at the National Institute of Standards and Technology 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.”

Citation: 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

Source: NIST

Explore further: Water leads to chemical that gunks up biofuels production

add to favorites email to friend print save as pdf

Related Stories

Molecular snapshots of oxygen formation in photosynthesis

Jul 11, 2014

Researchers from Umeå University, Sweden, have explored two different ways that allow unprecedented experimental insights into the reaction sequence leading to the formation of oxygen molecules in photosynthesis. ...

Recommended for you

The fluorescent fingerprint of plastics

18 minutes ago

LMU researchers have developed a new process which will greatly simplify the process of sorting plastics in recycling plants. The method enables automated identification of polymers, facilitating rapid separation ...

Water and sunlight the formula for sustainable fuel

4 hours ago

An Australian National University (ANU) team has successfully replicated one of the crucial steps in photosynthesis, opening the way for biological systems powered by sunlight which could manufacture hydrogen ...

Rice chemist wins 'Nobel Prize of Cyprus'

4 hours ago

Rice University organic chemist K.C. Nicolaou has earned three prestigious international honors, including the Nemitsas Prize, the highest honor a Cypriot scientist can receive and one of the most prestigious ...

Researchers create engineered energy absorbing material

6 hours ago

( —Materials like solid gels and porous foams are used for padding and cushioning, but each has its own advantages and limitations. Gels are effective as padding but are relatively heavy; gel performance ...

Solar fuels as generated by nature

6 hours ago

( —Society's energy supply problems could be solved in the future using a model adopted from nature. During photosynthesis, plants, algae and some species of bacteria produce sugars and other energy-rich ...

User comments : 0