An international group of researchers, including Brazilian scientists affiliated with the University of Campinas (UNICAMP), have succeeded in producing from hematite, one of the most common minerals on earth and the main source of iron, a new material christened “hematene”. The three-atom thick hematene is a ferromagnetic material, as opposed to the ore from which it was created and it can act as a photocatalyst to split water into hydrogen and oxygen, so that electricity can be generated from hydrogen, for example, as well as having several other potential applications.
While native hematite is antiferromagnetic, hematene is ferromagnetic, like a common magnet. In ferromagnets, the dipoles are parallel and aligned in the same direction. In antiferromagnets, the dipoles are antiparallel and aligned in opposite directions.
The researchers also analyzed hematene’s photocatalytic properties — its capacity to increase the speed of a chemical reaction when energized by light. The results showed that photocatalysis by hematene is more efficient than photocatalysis by hematite, whose photocatalytic properties are well-known but not strong enough to be useful.
For a material to be an efficient photocatalyst, it must absorb the visible part of sunlight, generate an electrical charge, and transport it to the surface of the material to carry out the desired reaction.
Hematite absorbs sunlight from the ultraviolet to the yellow-orange region, but the charge it produces is very short-lived. As a result, it fades before reaching the surface.
Hematene photocatalysis is more efficient because photons generate both negative and positive charges within a few atoms of the surface.