Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Calculations reveal fine line for hydrogen release from storage materials

17.07.2012
UC Santa Barbara scientists calculate microscopic reaction mechanisms in promising energy storage material aluminum hydride – and challenge outdated reaction curve interpretations

Hydrogen, the simplest and most abundant element on Earth, is a promising energy carrier for emerging clean energy technology. Hydrogen is the energy carrier that powers fuel cells in electric cars, and can be used to store energy generated by renewable sources at times of low demand.


Hydrogen vacancy clustering in aluminum hydride (AlH3): The dark blue atoms represent the Al atoms in the regular AlH3 lattice, and the light blue atoms represent the Al atoms in the Al-rich region created by the clustering of hydrogen vacancies as hydrogen leaves the material. Credit: Van de Walle Group

A major challenge with hydrogen energy is meeting the dual goals of high storage density and efficient kinetics for hydrogen release when it is needed.

Scientists at the University of California, Santa Barbara, have shed new light on the kinetics of hydrogen release, or dehydrogenation, from aluminum hydride (AlH3), a material that is highly promising for energy storage. Their computer simulations also illuminate the basic mechanisms governing these chemical reactions in general.

"Aluminum hydride turns out to be promising because the binding energy for hydrogen is low, so that the release rate can be fast," explained Chris Van de Walle, a professor in the Materials Department and head of the Computational Materials group at UCSB. "At the same time, kinetic barriers are high enough to prevent the hydrogen release rate from being too fast."

Drs. Lars Ismer and Anderson Janotti in the Computational Materials group used computer simulations to investigate the microscopic mechanisms that drive hydrogen release from aluminum hydride. They performed cutting-edge, first-principles calculations to examine how individual hydrogen atoms diffuse through the aluminum hydride — a process they found to be enabled by the creation of hydrogen vacancies. Their findings were detailed in a paper "Dehydrogenation of AlH3 via the Vacancy Clustering Mechanism" published in The Journal of Physical Chemistry.

Hydrogen vacancies are defects that play an important role – they enable diffusion. If every atom is in place, none of the atoms would be able to move. If a hydrogen atom is missing, a neighboring hydrogen atom can jump into that vacancy, thus enabling motion of hydrogen through the material.

The group then extracted key parameters from these highly sophisticated calculations, and used them in Kinetic Monte Carlo simulations aimed at modeling how hydrogen is released, leaving clusters of aluminum atoms behind.

"This multi-scale approach allows us to take the highly accurate information obtained in the first-principles computations and employ it to model realistic system sizes and time scales," said Ismer. "We can monitor the nucleation and growth of the aluminum phase and the rate at which hydrogen is released."

An important feature of the simulations is that they allowed the researchers to identify the rate-limiting mechanism, which turned out to be the diffusion process. This result initially seemed to contradict conclusions from studies using the traditional interpretation of the observed S-shaped onset of the dehydrogenation curves, which ruled out diffusion as the rate-limiting factor. However, the UCSB team's simulations produced reaction curves in agreement with the measurements, while clearly indicating that the reaction is limited by diffusion of point defects.

"These concepts transcend the specific application to hydrogen-storage materials," said Van de Walle. "The broader lesson here is that caution should be exercised in drawing conclusions based solely on the shape of reaction curves. Those simple rules of thumb were developed back in the 1930s, when experiments were less sophisticated and computational studies were unheard of. Our present work strongly suggests that traditional assumptions based on the shape of reaction curves should be reexamined."

Professor Van de Walle's Computational Materials Group is affiliated with the Materials Department and the College of Engineering at UC Santa Barbara. The group explores materials for hydrogen storage and generation, complex oxides, nitride semiconductors, novel channel materials and dielectrics, and materials for quantum computing.

This research was supported by the U.S. Department of Energy.

Melissa Van De Werfhorst | EurekAlert!
Further information:
http://www.ucsb.edu

More articles from Materials Sciences:

nachricht Oriented hexagonal boron nitride foster new type of information carrier
25.05.2020 | Japan Advanced Institute of Science and Technology

nachricht A replaceable, more efficient filter for N95 masks
22.05.2020 | American Chemical Society

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Biotechnology: Triggered by light, a novel way to switch on an enzyme

In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".

Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...

Im Focus: New double-contrast technique picks up small tumors on MRI

Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.

researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...

Im Focus: I-call - When microimplants communicate with each other / Innovation driver digitization - "Smart Health“

Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.

When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...

Im Focus: When predictions of theoretical chemists become reality

Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.

Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...

Im Focus: Rolling into the deep

Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.

A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Aachen Machine Tool Colloquium AWK'21 will take place on June 10 and 11, 2021

07.04.2020 | Event News

International Coral Reef Symposium in Bremen Postponed by a Year

06.04.2020 | Event News

 
Latest News

German-British Research project for even more climate protection in the rail industry

28.05.2020 | Transportation and Logistics

A special elemental magic

28.05.2020 | Physics and Astronomy

Skoltech scientists get a sneak peek of a key process in battery 'life'

28.05.2020 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>