Liquid Metals: A Novel Possibility of Fabricating 2D Metal Oxides.

2D metal oxides (2DMOs) have been widely applied in the fields of electronic, magnetic, optical, and catalytic materials, owing to their rich surface chemistry and unique electronic structures. However, their further development faces challenges such as the difficulty in fabricating 2DMOs with unstable surface induced by strong surface polarizability, or the high cost and limited yield of the fabrication process. Recently, liquid metals have shown great potential in the fabrication of 2DMOs. The native oxide skin formed on the surface of liquid metals can be considered as a perfect 2D planar material. Due to the solubility, fluidity, and reactivity of liquid metals, they can act as the solvent, reactant, and interface in the fabrication of 2DMOs. Moreover, liquid metals undergo a liquid-solid phase transition, enabling them to be a symmetric matched substrate for growing high-quality 2DMOs. An insightful survey of the recent progress in this research direction is presented. The features of liquid metals including good solubility, chemical reactivity, weak interface force, and liquid-solid phase transitions are introduced in detail. Furthermore, strategies for the fabrication of 2DMOs by virtue of these features are summarized comprehensively. Finally, current challenges and prospects regarding the future development in the fabrication of 2DMOs via liquid metals are highlighted.