A solid, when immersed in liquid, makes the liquid surrounding the solid different from the rest of the bulk liquid at a molecular level. This layer was crucial in understanding various concepts of subjects from material science to biology. When the solid material has charge in it, similar to a battery’s electrode, the interfacial liquid can undergo further changes. But, elucidating the molecular structure at the interface between the solid and the liquid under the given conditions can be difficult.
For the first time now, researchers at the US Department of Energy’s Lawrence Berkeley National Lab noticed the molecular structure of water at the gold surface under different conditions of charging.
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.
Gold keeping as the chemically inert electrode and a little saline water as the electrolyte, the scientists used a different method of XAS (x-ray absorption spectroscopy to probe the interface and depict how the interfacial molecules are arranged.
“We are only really interested in a nanoscale interfacial region, and looking at the fluorescence photon signal we can’t tell the difference between the interface and the interior electrolyte molecules,” says Miquel Salmeron, the senior scientist.
The difficult part was to get hold of a signal which would be dominated by the interfacial region. The team made this possible through measurement of electron emissions since electrons were emitted from x-ray excited water molecules travel only distances measured in nanometer through matter. The electrons coming at the surface of the gold electrode could be detected as an electric current passing through a wire attached to it.
Reported in Science in a paper named “The structure of interfacial water on gold electrodes studied by x-ray absorption spectroscopy,”, the study shows the first time that science community has show a greater sensitivity in an in-situ environment when in working electrode conditions.