News ID: 14117
Published: 0453 GMT October 24, 2014

Molecular structure of water at gold electrodes revealed

Molecular structure of water at gold electrodes revealed

When a solid material is immersed in a liquid, the liquid immediately next to its surface differs from that of the bulk liquid at the molecular level. This interfacial layer is critical to our understanding of a diverse set of phenomena from biology to materials science.


When the solid surface is charged, just like an electrode in a working battery, it can drive further changes in the interfacial liquid.

Now, for the first time, researchers at the US Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) have observed the molecular structure of liquid water at a gold surface under different charging conditions, physorg said.

Miquel Salmeron, a senior scientist in Berkeley Lab's Materials Sciences Division (MSD) explains this in the context of a battery.

"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."

Berkeley Lab researchers have developed a method not only to look at the molecules next to the electrode surface, but to determine their arrangement changes depending on the voltage.

With gold as a chemically inert electrode and slightly-saline water as an electrolyte, Salmeron and colleagues used a new twist on x-ray absorption spectroscopy (XAS) to probe the interface and show how the interfacial molecules are arranged.

XAS itself is not new. In this process, a material absorbs x-ray photons at a specific rate as a function of photon energy. A plot of the absorption intensity as a function of energy is referred to as a spectrum which, like a fingerprint, is characteristic of a given material molecule and its chemical state.






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