Freestanding Borophene and Its Hybrids

Abstract

Borophene, an elemental metallic Dirac material is predicted to have unprecedented mechanical and electronic character. Need of substrate and ultrahigh vacuum conditions for deposition of borophene restricts its large‐scale applications and significantly hampers the advancement of research on borophene. Herein, a facile and large‐scale synthesis of freestanding atomic sheets of borophene through a novel liquid‐phase exfoliation and the reduction of borophene oxide is demonstrated. Electron microscopy confirms the presence of β12, X3, and their intermediate phases of borophene; X‐ray photoelectron spectroscopy, and scanning tunneling microscopy, corroborated with density functional theory band structure calculations, validate the phase purity and the metallic nature. Borophene with excellent anchoring capabilities is used for sensing of light, gas, molecules, and strain. Hybrids of borophene as well as that of reduced borophene oxide with other 2D materials are synthesized, and the predicted superior performance in energy storage is explored. The specific capacity of borophene oxide is observed to be ≈4941 mAh g−1, which significantly exceeds that of existing 2D materials and their hybrids. These freestanding borophene materials and their hybrids will create a huge breakthrough in the field of 2D materials and could help to develop future generations of devices and emerging applications.

2D Boron Sheets: Structure, Growth, and Electronic and Thermal Transport Properties

“…Experimental research revealed that the interaction between χ 3 borophene and Ag(111) was very weak . Monolayer freestanding χ 3 borophene was also realized by facile sonochemical exfoliation . From the phonon band dispersion in Figure , we also found that the cutoff frequency of those borophene sheets was about 1200–1400 cm −1 , comparable to that of graphene (1600 cm −1 ) .…”

“…Therefore, β 12‐ borophene is highly to be stabilized by a suitable substrate. Recent experiment showed that the freestanding β 12 borophene has parallel ridges rather than flat structure and the ridge was found to be important for the stability of this structure . Among these explored structures in this paper, only the flat χ 3 borophene sheet is stable without external strain.…”

“…Very recently, Ranjan et al reported that they have obtained freestanding borophene with mixed phases; this is a great step for the borophene. However, the results need more experimental verifications …”

“…But freestanding borophene with single crystalline is still not achieved; these properties and applications need verification by the experiments in future. However we noted that freestanding borophene with mixed phases has been achieved by very recent experiments …”

“…However we noted that freestanding borophene with mixed phases has been achieved by very recent experiments. [39] The unique structures, growth mechanisms, proposed electronic and thermal transport properties of borophene have attracted extensive attentions. [40][41][42][43] In this review, we introduce the history of borophene and summarize the theoretical and experimental progresses on borophene, in terms of structures, growth, and electronic and thermal transport properties.…”