On-Surface Synthesis of Bismuth Monolayers through Ice-Confined Redox Reactions

Area of Science:

• Materials Science
• Nanotechnology
• Chemistry

Background:

• Two-dimensional (2D) bismuth exhibits unique quantum spin Hall effects and ferroelectricity, ideal for next-generation electronics.
• Challenges in synthesizing 2D bismuth stem from the low structural anisotropy of bulk bismuth crystals, hindering traditional exfoliation or growth methods.

Purpose of the Study:

• To develop a novel bottom-up strategy for synthesizing high-quality 2D bismuth.
• To overcome the limitations of existing synthesis methods for 2D bismuth.
• To explore the potential of synthesized 2D bismuth in electrochemical CO2 reduction and other applications.

Main Methods:

• An ice-confined, bottom-up synthesis strategy involving kinetically controlled nucleation in liquid nitrogen (-196°C).
• Redox-driven anisotropic growth of 2D bismuth between ice and aluminum surfaces at -20°C.
• Characterization of the resulting surfactant-free, solution-processable 2D bismuth with micrometer lateral dimensions and atomic-level thickness.

Main Results:

• Successfully synthesized crystalline 2D bismuth sheets with micrometer-scale lateral dimensions and atomic-level thickness (72% are 1-3 layers thick).
• Demonstrated high efficiency in electrochemical CO2 reduction, achieving 95.6% formate Faraday efficiency due to 2D bismuth's oxophilic surfaces capturing CO2 and forming *OCHO intermediates.
• Extended the synthesis method to other 2D metals like silver, copper, and tellurium.

Conclusions:

• The ice-confined strategy provides an unprecedented route for producing high-quality 2D bismuth, overcoming previous synthesis challenges.
• Synthesized 2D bismuth shows significant promise for electrochemical CO2 reduction and catalysis.
• The versatile method opens new avenues for designing functional 2D materials for electronics and catalysis.