Hydrated ions have been found to have mysterious properties in New ion batteries or appear

Recently, Chinese scientists led the world in obtaining the first atom-level image of hydrated sodium ions and discovered an illusion effect of hydrated ion transport. This study is for topics such as ion battery development, seawater desalination, and biological ion channels.

Research has opened a new door.

This research was published on May 14 in the international top academic journal Nature. The results were completed by the Beijing University Quantum Materials Science Center, Jiang Xulimei, Gaoyi, Peking University School of Chemistry and Molecular Engineering, and Wangenge.

Unmask the most mysterious layer of water molecules.

Water is the most abundant, most familiar and least understood substance in nature. Why is water so mysterious? "This is related to its composition. One of the authors of the article's newsletter, Academician Wangenge of the Chinese Academy of Sciences, told reporters that because the hydrogen atom in the water molecule is the lightest atom in the periodic table of elements, it can not be directly studied using a simpler classical particle model. Instead, it needs to be "fully quantized" simulation, that is, its nucleus and electrons must be regarded as Quanta, which greatly increases the difficulty of research.

"The interaction of water with other substances is also a very complex process. One of the authors of the article's newsletter, Professor Jiangying of the Quantum Materials Science Center of Peking University's School of Physics, said that the most common is the hydration process of ions. When the salt is dissolved in water, the dissolved ions are not free in the water, but combined with water molecules to form a "cluster" called an ion hydrate. "Ion hydration can be said to be ubiquitous and plays an important role in many physical, chemical, and biological processes, such as salt dissolution, electrochemical reactions, ion transfer in the body of life, atmospheric pollution, seawater desalination, and corrosion. "

What kind of microstructure does ion hydrate have? How does it move? These issues have always been the focus of debate in the academic community. It is understood that as early as the end of the 19th century, people realized the existence of ion hydration and began systematic research, but after more than a hundred years of hard work, There are many problems such as the number of water-shell layers of ions, the number and configuration of water molecules in each water-complex layer, the influence of water-complex ions on the structure of hydrogen bonds, and the microscopic factors that determine the transport properties of water-complex ions.

Clear images of ion hydrates are seen for the first time.

In recent years, Wangenge and Jiangying have worked with colleagues and students to develop high-resolution scanning probe technology at the atomic level and full quantization calculation methods for light element systems, accumulating rich research. Experimental and theoretical basis.

To perform high-resolution imaging of hydrated ions on an atomic scale, it is first necessary to "separate" a single hydrated Ion.

This is a rather difficult matter. In order to solve this problem, the researchers developed a unique ion control technique based on a scanning tunneling microscope and developed a single ion hydrate -- using a very sharp metal needle tip on the surface of sodium chloride film. Moving, Drain a single sodium ion and then "drag" the water molecule to bind to it. This results in a single "sodium hydrate ion" containing different numbers of water molecules.

The next challenge is to determine the geometry of a single ion hydrate cluster by means of high-resolution imaging.

In response to this problem, the researchers developed a non-intrusive atomic force microscope imaging technology based on carbon monoxide needle-tip modification, which can rely on extremely weak high-level electrostatic forces to scan imaging. They applied this technique to the ion hydrate system, obtained the first atom-level resolution imaging, and successfully determined its atomic adsorption configuration.

This is the first time that an atom-level image of ion hydrates has been obtained in real space. And this image is quite clear: not only can the adsorption position of water molecules and ions be accurately determined, but even small changes in the orientation of water molecules can be directly identified. It can be said that spatial resolution almost reaches the limit of atoms.

Discover the wonderful kinetic "phantom number effect"

After obtaining microscopic images of Ionic hydrates, the researchers further studied their kinetic transport properties and found an interesting effect: when the surface of sodium chloride crystals moves, Sodium ion hydrates containing a specific number of water molecules seem to suffer from "hyperactivity disorder"-an unusually high diffusion capacity that is 10-100 times faster than other hydrates. The researchers call this characteristic the "phantom number effect" of dynamics.

Why is there such a strange phenomenon? Through simulation calculations, the researchers found that this phantom number effect was derived from the symmetry matching degree of Ionic hydrates with surface lattices. In simple terms, sodium ion hydrates containing 1, 2, 4, and 5 water molecules are easily "stuck" on the surface of sodium chloride crystals, while ion hydrates containing 3 water molecules are difficult to "stuck" because symmetry does not match the substrate. So it will "slide" on its surface very quickly.

This work established the direct correlation between the microscopic structure and transport properties of Ionic hydrates for the first time, refreshing the traditional understanding of ion transport in limited systems.

Hydrated ions become manageable. What can they bring us?

It is understood that this research work has been praised and appreciated by reviewers in three different fields of the journal Nature. They believe that this work "will immediately attract widespread interest in the field of theoretical and applied surface science" and "provide new ways to control the transport of hydrated ions on the surface on a nanoscale and can be expanded to other hydrated systems."

Academician Wangenge said: "The results of this study show that we can achieve the purpose of selectively increasing or weakening the transport capacity of certain ions by changing the symmetry and periodicity of the surface of the material. This has important potential significance for many related application fields. "

For example, a new type of ion battery can be developed. Jiangying told reporters that the lithium-ion batteries we use now typically consist of macromolecular polymers, and based on this new study, it will be possible to develop a new battery based on hydrated lithium-ion. "This battery will greatly increase the rate of ion transfer, which will shorten the charging time and increase the battery power. It will be more environmentally friendly and the cost will be greatly reduced. "

In addition, this result has also opened up a new way for research in the frontier areas such as corrosion prevention, electrochemical reactions, seawater desalination, and biological ion channels. At the same time, the high-precision experimental technology developed by this work is expected to be applied to more and more extensive hydrated materials systems in the future.

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