Comprehensive methodology for the synthesis of high-purity and exfoliated MoB MBene nanosheets

This work presents a comprehensive methodology for synthesizing chemically pure two-dimensional molybdenum boride (MoB MBene) with a controlled morphology. The precursor MoAlB MAB phase was successfully synthesized via a molten-salt-assisted solid-state reaction, as confirmed by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. An optimized two-step chemical etching protocol, involving treatment with hydrofluoric acid followed by boiling in a sodium hydroxide solution, effectively removed the aluminum layers and accompanying impurities (AlF3, Na2Al22O34), yielding a chemically pure MoB powder. For the effective exfoliation of multilayer MoB into nanosheets, a two-step mechanical procedure was employed, comprising of preliminary ball milling in isopropyl alcohol to weaken the interlayer bonds and subsequent ultrasonication. The resulting exfoliated MoB MBene nanosheets exhibit an average lateral size of ∼60 nm and an average thickness of ∼4 nm, corresponding to a few atomic layers. The phase composition and high crystallinity of the exfoliated particles were confirmed by XRD and selected area electron diffraction (SAED) methods. The high yield of exfoliated particles (80–85 %) demonstrates the effectiveness of the developed methodology.