Chemical Processing Methods for Deintercalation and Exfoliation of NaCrO2

Abstract

Chemical exfoliation of non-van der Waals (non-vdW) materials can be beneficial as an easily scalable method of obtaining high quality nanosheets, but is difficult due to the stronger interlayer bonds as compared to vdW compounds. Of the non-vdW materials, alkali-intercalated layered materials are a good candidate for exfoliation because they are quasi-2D, but previous research often focused on chalcogenide-based materials, thus leaving the effects of chemical processes on oxide-based ones unclear. In this work, we study the deintercalation and exfoliation of NaCrO₂ after three chemical processes: proton exchange, solvent reaction, and oxidative extraction. All resulting materials show different magnetic behavior compared to the parent material. Proton exchange and solvent reaction were both combined with a subsequent sonication step to make 3-4 nm thick Cr₂O₃ nanosheets. Finally, we compare the behavior of NaCrO₂ to NaCrS₂ to understand the differences in how oxides and chalcogenides behave. Our work demonstrates the structural complexity that can result from these deceptively simple chemical processing methods and how this can affect subsequent exfoliation.