Brazilian scientists from University of Campinas (UNICAMP) have developed a new 2D material from ordinary iron ore that has huge potential for solar cells. The new material is called hematene, which is only three atoms thick and has photocatalytic properties. The research on the new material was conducted at the Center for Computational Engineering and Sciences.
International group of researchers including Brazilian scientists obtain new material from iron ore with application as a photocatalyst. Source: UNICAMP
"The material we synthesized 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," said Douglas Soares Galvão, one of the authors of the study and co-principal investigator at CCES.
The new material was exfoliated out of hematite, one of the most common minerals on Earth and one of the main sources of iron. Hematite is a non-van der Waals material. This means it is held together by 3D bonding networks that are highly oriented large crystals. All this means that hematite is a great precursor for the exfoliation of novel 3D materials.
"Most of the 2D materials synthesized to date were derived from samples of van der Waals solids. Non-van der Waals 2D materials with highly ordered atomic layers and large grains are still rare," Galvão said.
Hematene is synthesized by the liquid-phase exfoliation of hematite ore with the organic solvent N, N-dimethylformamide (DMF). Transmission of electron microscopy confirmed that the exfoliation and formation of hematene in sheets with the thickness of three iron and oxygen atoms in randomly stacked sheets.
Native hematite is an anti-ferromagnetic material but hematene is a ferromagnetic material. The magnetic properties of the two materials are completely different.
"In ferromagnets, the atoms' magnetic moments point in the same direction. In antiferromagnets, the moments in adjacent atoms alternate," Galvão explained.
Hematene’s photocatalytic properties -- its capacity to increase the speed of chemical reaction when it is energized by light -- were further studied at UNICAMP. This proved that hematene photocatalysts are more efficient than hematite photocatalysis.
A photocatalyst must absorb the visible part of sunlight in order to generate an electrical charge and then transport it to the surface of a material. The problem with hematite is that even though it does absorb sunlight from the ultraviolet to the yellow-orange region, it is unable to hold the charge. The charge has mostly dissipated by the time it reaches the surface.
The hematene photocatalysis can generate negative and positive charges that are more effective and last longer than the hematite photocatalysis. When the hematene photocatalysis is paired with titanium dioxide nanotube arrays, easy pathways for electrons are created.
The paper on the new 2D material was published in Nature Nanotechnology.
