light-absorbing materials. Photo: DTU

Stepping up the hunt for materials to harvest solar energy

Monday 02 Feb 15
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Karsten Wedel Jacobsen
Professor
DTU Physics
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An intense hunt is currently underway for materials with the capacity to transform sunlight into fuels. The volume of materials is overwhelming, however, so researchers need reliable methods to speed their progress in the search for good, light-absorbing materials, for example. Researchers at DTU Physics have now established just such a method.

By Anne Hansen

One of the most promising methods for exploiting solar energy—and, as a result, a potential solution to problems associated with highly polluting and increasingly scarce fossil fuels—is to use energy from the sun to split water and thus generate new fuels. The process of absorbing sunlight and then splitting water (or another material) is called photocatalysis.

Three things at once
However, using photocatalysis to split water requires a material that absorbs not only as much sunlight as possible, but also the entire visible section of the light spectrum. And to make a real difference in the field of global energy consumption, this material must, of course, be inexpensive as well. Unfortunately, materials of this kind are few and far between.

Like hunting for a needle in a haystack
The search for a good photocatalytic material can best be compared to the medical community’s hunt for a cure for cancer or a vaccine to wipe out Ebola. In the same way as the pharmaceutical industry needs methods for rapidly screening of thousands of possible combinations of substances—of which perhaps only one has the perfect properties—energy researchers need fast and reliable methods for examining materials and identifying those best suited to splitting water. These materials can then be subjected to more detailed and time-consuming analyses.

“When we’re trying to find a material that we can use to split, it’s a bit like looking for a needle in a haystack. The experimental databases feature tens of thousands of materials and list all kinds of details such as their crystal structures or their magnetic and electrical properties. But when it comes to the issue of how good the materials are at powering the process of splitting water, there is little—if any—information to be found,” relates Professor Karsten Wedel Jacobsen from DTU Physics.

New tool for seeking out suitable materials
In partnership with researchers from MIT and the Lawrence Berkeley National Laboratory, DTU researchers have now described a method for screening material databases quickly and reliably. Their findings have recently been published in the recognized journal Advanced Energy Materials, which even put the DTU researchers on the cover of the hard-copy version of its February issue.
Working with a database containing 2,400 materials whose crystal structures were known, but whose capacity in relation to splitting water was not, the researchers demonstrated that a fast theoretical calculation method can be reliably used to identify materials with good light-harvesting and water-splitting properties. From the 2,400 materials examined, the researchers found 25 ‘interesting candidates’, and closer analysis revealed that five of these could realistically be used as photocatalytic materials.

“We hope that our procedure will prove useful in the hunt for new and improved methods of utilizing solar energy,” concluded Karsten Wedel Jacobsen.

Read the article:
New Light-Harvesting Materials Using Accurate and Efficient Bandgap Calculations
 Ivano E. Castelli, Falco Hüser, Mohnish Pandey , Hong Li , Kristian S. Thygesen , Brian Seger, Anubhav Jain, Kristin A. Persson, Gerbrand Ceder, and Karsten W. Jacobsen
Advanced Energy Materials 2015, 5, 1400915

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