Insomniac iron oxide (rust) electrons and environmentally friendly semiconductors

The Sept. 7, 2012 news item by Lynn Yarris for physorg.com highlights some research on rust being conducted (pun intended) at Lawrence Berkeley National Laboratory (Berkeley Labs).

Rust – iron oxide – is a poor conductor of electricity, which is why an electronic device with a rusted battery usually won’t work. Despite this poor conductivity, an electron transferred to a particle of rust will use thermal energy to continually move or “hop” from one atom of iron to the next. Electron mobility in iron oxide can hold huge significance for a broad range of environment- and energy-related reactions, including reactions pertaining to uranium in groundwater and reactions pertaining to low-cost solar energy devices.  …

“We believe this work is the starting point for a new area of time-resolved geochemistry that seeks to understand chemical reaction mechanisms by making various kinds of movies that depict in real time how atoms and electrons move during reactions,” says Benjamin Gilbert, a geochemist with Berkeley Lab’s Earth Sciences Division and a co-founder of the Berkeley Nanogeoscience Center who led this research. “Using ultrafast pump-probe X-ray spectroscopy, we were able to measure the rates at which electrons are transported through spontaneous iron-to-iron hops in redox-active iron oxides. Our results showed that the rates depend on the structure of the iron oxide and confirmed that certain aspects of the current model of electron hopping in iron oxides are correct.”

The news item provides a wealth of detail about electron hopping and iron oxide but I was most intrigued by future applications,

Katz [Jordan Katz, the lead author, now with Denison University]  is excited about the application of these results to finding ways to use iron oxide for solar energy collection and conversion.

“Iron oxide is a semiconductor that is abundant, stable and environmentally friendly, and its properties are optimal for absorption of sunlight,” he says. “To use iron oxide for solar energy collection and conversion, however, it is critical to understand how electrons are transferred within the material, which when used in a conventional design is not highly conductive. Experiments such as this will help us to design new systems with novel nanostructured architectures that promote desired redox reactions, and suppress deleterious reactions in order to increase the efficiency of our device.”

I find rust quite attractive although, admittedly, very irritating at times. I have never before considered the possibility it might prove useful nor had I realized that it never rests (sleeps).

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