Structure, Stability, and Electronic Properties of Hydrogenated Monolayer 2D Silicon Allotropes by First-Principles Calculation

Due to silicon having a sp(3) hybridization configuration in nature, most monolayer 2D silicon allotropes have to be proposed based on the dumbbell-like units to ensure their structural stability. Herein, hydrogenated monolayer 2D silicon allotropes are predicted, and the sp(3) configuration of structures is guaranteed by covering the surface with hydrogen. Compared with the corresponding hydrogen-free structures and the hydrogen-free structures on Ag(111) substrate, these predicted structures have lower formation energies, indicating that these monolayer 2D silicon allotropes can be obtained by hydrogenation reactions. These predicted structures are all dynamically stable and structures SCH, HPH, and HDH are thermodynamically stable. The structure SLH is the transition-state structure of structure SCH and structures OTQTH and HHKH are metastable structures. The stable and metastable structures are all semiconductors and can be applied to semiconductor devices. All of these monolayer 2D silicon allotropes have high gravimetric hydrogen contents and may have applications for chemical hydrogen storage or water-enabled H-2 production. It is believed that the results of this work have a good reference value for the experimental synthesis of hydrogenated monolayer 2D silicon allotropes, and have reference significance for understanding the diversity and electronic properties of hydrogenated monolayer 2D silicon allotropes.