Ultrathin Single Crystalline MgO(111) Nanosheets*

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Synthesizing high-quality, single-crystalline two-dimensional (2D) nanomaterials from nonlayered metal oxides presents significant challenges.
• Achieving long-range single-crystallinity and clean, high-energy surfaces is crucial for advanced material applications.

Purpose of the Study:

• To develop a method for synthesizing single-crystalline magnesium oxide (MgO) nanosheets with defined crystallographic orientation.
• To characterize the surface properties and reactivity of the synthesized MgO nanosheets.

Main Methods:

• A two-step synthesis approach was employed, starting with the formation of ultrathin magnesium hydroxide (Mg(OH)2) nanosheets.
• Selective topotactic conversion of the Mg(OH)2 precursor to MgO(111) nanosheets was achieved through heating under dynamic vacuum.

Main Results:

• Successfully synthesized single-crystalline MgO(111) nanosheets, overcoming challenges in nonlayered metal oxide 2D material fabrication.
• The defect-rich MgO surface features terminal -OH groups, three-coordinated O2- sites, low-coordinated Mg2+ sites, and trapped electrons at oxygen vacancies.
• Demonstrated high reactivity of MgO nanosheets, evidenced by low-temperature activation of carbon monoxide (CO) and formation of strongly adsorbed red-shifted CO and C2 species.

Conclusions:

• The developed method enables the synthesis of high-quality, single-crystalline MgO(111) nanosheets.
• The unique surface defects and low-coordinated sites on MgO nanosheets contribute to their exceptional catalytic activity.
• These reactive MgO nanosheets show promise for applications in catalysis and surface chemistry.