A geochemical mystery that has haunted scientists for almost a century may be solved. Researchers theorize that light elements that are in short supply on our planet’s surface are “hidden” in the solid inner core in a special form of iron called electride. This discovery not only explains the structure of the Earth, but also promises a breakthrough in the creation efficient catalysts for industry.
For decades, scientists could not understand where light elements disappeared from our planet. Compared to the Sun and meteorites, Earth has significantly less hydrogen, carbon, nitrogen, sulfur and noble gases. Some of the losses were attributed to the process of planet formation, but this was not enough to explain.
A new hypothesis proposed by an international team of researchers states that these elements are located at the very center of the Earth – in its solid inner core. At a monstrous pressure of 3.6 million atmospheres, iron there transforms into a special state of electride. In this form, the metal is able to capture and hold atoms of light elements within its crystal lattice.
This explains seismology data: The density of the inner core is 5–8% lower than it would be if it consisted only of pure iron. The process of “absorption” of elements may have continued for billions of years and is still ongoing.
The discovery is not only fundamental, but also of great practical importance. Electrides are materials in which electrons are not attached to atoms, but are captured in special “traps” in the space between them. These free electrons can be easily donated to participate in chemical reactions, making electrides ideal catalysts.
One such catalyst, based on the mineral mayenite, is already used in Japan to produce ammonia, a key component of fertilizers. This process consumes 20% less energy than the traditional Haber-Bosch method, which alone is responsible for 2% of global energy consumption.
Scientists are actively searching for new electrides. Just recently, a calcium-based organic electride was accidentally discovered that could replace expensive palladium catalysts in the production of pharmaceuticals. To search for such materials they now involve artificial intelligence, which analyzes the structures of thousands of compounds in search of the desired “electron traps.”
The study of electrides combines the solution of a deep scientific mystery about the structure of our planet and the creation of future technologies. Understanding these unique materials opens the way to an energy-efficient chemical industry, “green” synthesis of fertilizers and medicines, and in the future, may even change the approach to radioactive waste disposal.
Source: Live Science
Image: CHRISTOPH BURGSTEDT
