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

Abstract

2D bismuth possesses a unique combination of properties, such as cryogenic-free quantum spin Hall effects and intrinsic single-element ferroelectricity, making it highly promising for next-generation electronic devices. However, the synthesis of 2D bismuth via exfoliation or direct growth is hindered by the low structural anisotropy of bulk bismuth crystals. To address this challenge, we demonstrate an unprecedented ice-confined bottom-up strategy for growing 2D bismuth. This approach involves kinetically controlled nucleation in liquid nitrogen (-196 °C), followed by redox-driven anisotropic growth within the confined space between ice and aluminum surfaces at -20 °C. The surfactant-free process yields solution-processable crystalline 2D bismuth with micrometer-scale lateral dimensions and atomic-level thickness, where 72% of the sheets are 1-3 layers thick. Thanks to its oxophilic surfaces, the as-grown 2D bismuth effectively captures CO₂ molecules and facilitates their conversion to *OCHO intermediates during electrochemical CO₂ reduction, leading to an excellent formate Faraday efficiency of 95.6%. Moreover, this versatile synthetic route can be extended to other functional 2D metals, including silver, copper, and tellurium, thereby opening new avenues for the design of advanced catalysis, electronics, and related technologies.