Molecular Structure of Water at Gold Electrode Unearthed For the First Time

Whenever a solid is dipped in liquid, the liquid next to the object is molecularly unlike than the bulk of the liquid. If the surface is charged, this dissimilarity can increase even further. In the past it was difficult to understand the molecular structure of the solid-liquid interface. However this is exactly what has been achieved by the researchers at the DOE/Lawrence Berkeley National Laboratory.

Researchers have been able to observe the molecular structure of liquid water at gold surface in varying charging conditions. The discovery was published in a recent edition of the journal Science. The discovery will have immense potential and will help researchers understand a variety of biological phenomenon.

Miquel Salmeron, a senior scientist in Berkeley Lab’s Materials Sciences Division (MSD) and professor in UC Berkeley’s Materials Science and Engineering Department said, “At an electrode surface, the build-up of electrical charge, driven by a potential difference (or voltage), produces a strong electric field that drives molecular rearrangements in the electrolyte next to the electrode.”

To determine the arrangement of the molecules next to the electrode surface the researchers used x-ray spectroscopy to probe the interface. The problem was that the XAS technique required the process to be carried out in vacuum and this caused the liquid to evaporate. To get over this problem the researchers made use of a very thin x-ray transparent window in the order of 100 nm, or a tenth of a micrometer with a thin coating of Gold. With this arrangement, the team was able to exposé the water molecules to x-ray without any risk of it getting evaporated.

It was critical for the researchers to determine which part of the current was caused by the x-rays or battery. To achieve this researchers “pulsed the incoming x-rays from the synchrotron at a known frequency,” which enabled the researchers to segregate the current. The experiment enabled the team to achieve absorption vs. x-ray energy curves (spectra) that explained how water molecules within the nanometers of the gold surface absorbed the X-ray. Finally employing a supercomputer the researchers conducted simulations of the gold-water interface. The x-ray absorption spectra of the predicted structures were calculated.

David Prendergast, a staff scientist in the Molecular Foundry and researcher in the Joint Center for Energy Storage Research (JCESR) explained, “These are first-principles calculations. We don’t dictate the chemistry: we just choose what atomic elements are present and how many atoms. That’s it. The chemistry is a result of the calculation. The main thing we know about the gold electrode surface from the x-ray absorption spectra: how many water molecules are tilted one way or another, and if their hydrogen bonds are broken or not. Water next to the electrode has a different molecular structure than it would in the absence of the electrode.”

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Roxanne Briean

I am a geek, a gamer and a writer. I have always been fascinated with the online community. At the moment I work as a full-time writer and study interior design. When I'm not scouring the net in search of interesting new gadgets and software I spend my time in MOBAs or drawing.