Hematene Material Shows Promise for Solar Fuel Generation

Hematene created by a Rice University-led team is the first known 2D non-van der Waals material. The transmission electron image shows a single sheet of hematene. Scale bar equals 0.5 μm. Image courtesy Shyam Sinha and Peter van Aken/Max Planck Institute for Solid State Research, Stuttgart, Germany

An international team of scientists led by Rice University (Houston) researchers has created a new 2D hematene material, an atomically thin form of the common iron oxide known as hematite, which holds potential for 2D magnetism and efficient light-assisted water splitting. In the wake of the team’s recent discovery of a flat form of gallium, the team’s latest discovery is this new 2D material that the researchers said could be a game-changer for solar fuel generation.

Rice materials scientist Pulickel Ajayan and colleagues extracted 3-atom-thick hematene from common iron ore, and the researchers published their findings May 7 in the journal Nature Nanotechnology. An abstract of the paper can be found at http://dx.doi.org/10.1038/s41565-018-0134-y.

Hematene may be an efficient photocatalyst, especially for splitting water into hydrogen and oxygen, and could also serve as an ultrathin magnetic material for spintronic-based devices, according to the Rice researchers. “Two-dimensional magnetism is becoming a very exciting field with recent advances in synthesizing such materials, but the synthesis techniques are complex and the materials’ stability is limited,” Ajayan said. “Here, we have a simple, scalable method, and the hematene structure should be environmentally stable.”

Ajayan’s lab worked with researchers at the University of Houston and in India, Brazil, Germany and elsewhere to exfoliate the material from naturally occurring hematite using a combination of sonication, centrifugation, and vacuum-assisted filtration. Hematite was already known to have photocatalytic properties, but they are not good enough to be useful, the researchers said.

“For a material to be an efficient photocatalyst, it should absorb the visible part of sunlight, generate electrical charges and transport them to the surface of the material to carry out the desired reaction,” said Oomman Varghese, a co-author of the paper and associate professor of physics at the University of Houston. “Hematite absorbs sunlight from ultraviolet to the yellow-orange region, but the charges produced are very short-lived. As a result, they become extinct before they reach the surface.”

Read more: New 2D Hematene Material Shows Promise for Solar Fuel Generation

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