Researchers watch molecules in a light-triggered catalyst ring 'like an ensemble of bells'

phys.org | 2/22/2019 | Staff
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Photocatalysts – materials that trigger chemical reactions when hit by light – are important in a number of natural and industrial processes, from producing hydrogen for fuel to enabling photosynthesis.

Now an international team has used an X-ray laser at the Department of Energy's SLAC National Accelerator Laboratory to get an incredibly detailed look at what happens to the structure of a model photocatalyst when it absorbs light.

Researchers - Laser - Pulses - Structure - Change

The researchers used extremely fast laser pulses to watch the structure change and see the molecules vibrating, ringing "like an ensemble of bells," says lead author Kristoffer Haldrup, a senior scientist at Technical University of Denmark (DTU). This study paves the way for deeper investigation into these processes, which could help in the design of better catalysts for splitting water into hydrogen and oxygen for next-generation energy technologies.

"If we can understand such processes, then we can apply that understanding to developing molecular systems that do tricks like that with very high efficiency," Haldrup says.

Results - Week - Physical - Review - Letters

The results published last week in Physical Review Letters.

The platinum-based photocatalyst they studied, called PtPOP, is one of a class of molecules that scissors hydrogen atoms off various hydrocarbon molecules when hit by light, Haldrup says: "It's a testbed – a playground, if you will – for studying photocatalysis as it happens."

SLAC - Laser - Linac - Coherent - Light

At SLAC'S X-ray laser, the Linac Coherent Light Source (LCLS), the researchers used an optical laser to excite the platinum-containing molecules and then used X-rays to see how these molecules changed their structure after absorbing the visible photons. The extremely short X-ray laser pulses allowed them to watch the structure change, Haldrup says.

The researchers used a trick to selectively "freeze" some of the molecules in their vibrational motion, and then used the ultrashort X-ray pulses to capture how the entire ensemble of molecules evolved in time after being hit with...
(Excerpt) Read more at: phys.org
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