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January 2012

Rust Splits Water!

Understanding water splitting on an iron oxide surface opens the door to a new line of research in hydrogen production

Sanchita Biswas

Using scanning tunneling microscopy, a clean iron surface (left) and the one dosed with water (center) are shown.  A simple schematic (right)  diagram shows the adsorption of water molecules on the surface and possible movement and loss of the OH.

Efficient water splitting holds immense promise as a way to produce hydrogen for clean, sustainable energy conversion processes. Scientists working in the Center for Atomic-Level Catalyst Design, or CALCD, discovered that a form of rust, magnetite (Fe3O4), one of the most abundant materials in the Earth’s crust, performs water splitting at room temperature without the need for electricity or light to drive the reaction.

Significant increases in federal government funding in the alternative energy research field also reflect the importance of it to deal with the ever-increasing global energy demand, limited natural resources and climate change concerns.

Where did all the oxygen go?

The research team discovered the water-splitting reaction while studying the surface of magnetite in an ultra-high vacuum environment. They noticed that when they exposed the magnetite surface to small amounts of water (H-O-H), only one hydrogen atom from the water molecule was visible in atomically resolved images of the surface; the remaining OH from the water had vanished.

“For a long time we assumed that the OH was really there and just somehow invisible in the STM images,” explained Gareth Parkinson, lead author on the paper.

To solve the mystery, they dosed labeled water (H218O) on the magnetite surface and performed ion-scattering experiments, which revealed no trace of the 18O oxygen atoms on the surface.

“Taken together, these experiments point to the intriguing possibility that the Fe3O4 surface might split water at room temperature,” says Ulrike Diebold, who led the research team at the Vienna University of Technology, a partner institution in CALCD.

With the experimental evidence that the magnetite surface irreversibly splits water in hand, the team explains that the most likely scenario is that water initially splits into H and OH species, and then the OHs react with each other to create species that are not bound to the magnetite surface at room temperature.

What’s next?

The team is investigating, both experimentally and theoretically, in collaboration with theorist Dave Sholl (Georgia Tech, from the CALCD), the nature of the gaseous products from the surface to validate the model and better understand how this surprising reaction mechanism takes place.

More Information

Parkinson GS, Z Novotný, P Jacobson, M Schmid and U Diebold. 2011. “Room Temperature Water Splitting at the Surface of Magnetite.” Journal of the American Chemical Society 133(32):12650-12655. DOI: 10.1021/ja203432e.

Acknowledgments

This work was supported by the CALCD, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

About the author(s):

  • Sanchita Biswas is a postdoctoral researcher at Louisiana State University and a member of the Center for Atomic-Level Catalyst Design, an Energy Frontier Research Center. She received her Ph.D. in chemistry from the University of Central Florida in 2010. Her research interests are in the design, synthesis and evaluation of nanomaterials, based on organic polymers and atomically precise inorganic metal nanoclusters using “lab-on-a-chip” devices, for potential biomedical, catalysis and energy applications.

Rescued by Rust?

A fundamental discovery about iron could lead to affordable hydrogen for fuel cells

Using scanning tunneling microscopy, a clean iron surface (left) and the one dosed with water (center) are shown.  A simple schematic (right)  diagram shows the adsorption of water molecules on the surface and possible movement and loss of the OH.

With the ever-increasing global energy demand, limited natural resources and climate concerns, fuel cells offer an intriguing option. However, they require a source of hydrogen that is generated with little need for electricity or light. Creating the hydrogen cannot require more energy than the fuel cell produces. Scientists discovered that a form of iron rust, magnetite, one of the most abundant materials in the Earth’s crust, can split water into hydrogen and oxygen at room temperature without the need for electricity or light. This work could break through a key barrier in hydrogen production for fuel cells. The Center for Atomic-Level Catalyst Design, led by Louisiana State University, conducted the research.

More Information

Parkinson GS, Z Novotný, P Jacobson, M Schmid and U Diebold. 2011. “Room Temperature Water Splitting at the Surface of Magnetite.” Journal of the American Chemical Society 133(32):12650-12655. DOI: 10.1021/ja203432e.

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.