Sandwiched Epitaxy Growth of 2D Single-Crystalline Hexagonal Bismuthene Nanoflakes for Electrocatalytic CO2 Reduction

Two-dimensional (2D) bismuthene is predicted to possess intriguing physical properties, but its preparation remains challenging due to the high surface energy constraint. Herein, we report a sandwiched epitaxy growth strategy for the controllable preparation of 2D bismuthene between a Cu foil substrate and a h-BN covering layer. The top h-BN layer plays a crucial role in suppressing the structural transformation of bismuthene and compensating for the charge transfer from the bismuthene to the Cu(111) surface. The bismuthene nanoflakes present a superior thermal stability up to 500 C-degrees in air, attributed to the passivation effect of the h-BN layer. Moreover, the bismuthene nanoflakes demonstrate an ultrahigh faradaic efficiency of 96.3% for formate production in the electrochemical CO2 reduction reaction, which is among the highest reported for Bi-based electrocatalysts. This study offers a promising approach to simultaneously synthesize and protect 2D bismuthene nanoflakes, which can be extended to other 2D materials with a high surface energy.

Automated summary

A new method for the preparation of two-dimensional bismuthene nanoflakes, along with their protection and application in electrochemical CO2 reduction, is proposed in this study. The method involves the use of a h-BN covering layer to suppress structural transformations and charge transfer, resulting in improved thermal stability and electrocatalytic performance. This research is of significant importance for the synthesis and utilization of high surface energy two-dimensional materials.