ORNL's Huiyuan Zhu places a sample of boron nitride, or white graphene, into a furnace as part of a novel, nontoxic gas exfoliation process for separating 2D nanomaterials. Photo: ORNL.A team of scientists led by the US Department of Energy's Oak Ridge National Laboratory (ORNL) has developed a novel way to produce two-dimensional (2D) nanosheets by separating bulk materials with nontoxic liquid nitrogen. By generating a 20-fold increase in surface area per sheet, this environmentally-friendly process could expand the nanomaterials' commercial applications.
"It's actually a very simple procedure," explained ORNL chemist Huiyuan Zhu, who co-authored a paper on this work in Angewandte Chemie International Edition. "We heated commercially-available boron nitride in a furnace to 800°C to expand the material's 2D layers. Then, we immediately dipped the material into liquid nitrogen, which penetrates through the interlayers, gasifies into nitrogen, and exfoliates, or separates, the material into ultrathin layers."
Nanosheets of boron nitride, also known as white graphene, could be used for various applications in separation and catalysis, such as transforming carbon monoxide to carbon dioxide in gasoline-powered engines. In addition, these nanosheets could act as an absorbent to mop up hazardous waste. Zhu said that the team's controlled gas exfoliation process could also be used to help synthesize other 2D nanomaterials such as graphene, which has potential applications in semiconductors, photovoltaics, electrodes and water purification.
Because of the versatility and commercial potential of one-atom-thick 2D nanomaterials, scientists are seeking more efficient ways to produce larger sheets. Current exfoliation procedures use harsh chemicals that produce hazardous by-products and reduce the amount of surface area per nanosheet, Zhu said.
"In this particular case, the surface area of the boron nitride nanosheets is 278m2 per gram, [while] the commercially-available boron nitride material has a surface area of only 10m2 per gram," Zhu said. "With 20 times more surface area, boron nitride can be used as a great support for catalysis."
Zhu and her colleagues are now planning to expand the surface area of the boron nitride nanosheets still further, and also to test their feasibility in cleaning up engine exhaust and improving the efficiency of hydrogen fuel cells.
This story is adapted from material from ORNL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.