The shape-dependent surface oxidation of 2D ultrathin Mo2C crystals.

Lin Li,Jonas Baltrusaitis,Min Gao,Dong Shi

doi:10.1039/c9na00504h

Abstract

2D atomic crystals have been widely explored, usually owing to their numerous shapes, of which the typical hexagon has drawn the most interest. However, the relationship between shape and properties has not been fully probed, owing to the lack of a proper system. Here, we demonstrate for the first time the shape-dependent surface oxidation of 2D Mo2C crystals, where the elongated flakes are preferentially oxidized under ambient conditions when compared with regular ones, showing higher chemical activity. The gradual surface oxidation of elongated Mo2C crystals as a function of time is clearly observable. Structural determinations reveal that a discrepancy in the arrangement of Mo and C atoms between elongated and regular crystals accounts for the selective oxidation behavior. The identification of the shape-dependent surface oxidization of Mo2C crystals provides significant possibilities for tuning the properties of 2D materials via shape-control.

Highlights

We demonstrate for the first time the shape-dependent surface oxidation of 2D Mo2C crystals, where the elongated flakes are preferentially oxidized under ambient conditions when compared with regular ones, showing higher chemical activity
Structural determinations reveal that a discrepancy in the arrangement of Mo and C atoms between elongated and regular crystals accounts for the selective oxidation behavior
As a new member of this family, transition metal carbides (TMCs) have emerged,[9,10,11] which combine the properties of metals and covalent compounds, owing to their good mechanical stability and high electrical and thermal conductivity

Summary

Introduction

In the past few years, the eld of 2D materials has witnessed an explosive development, with novel materials produced, and unusual properties demonstrated.[1,2,3,4] Of those newly-developed 2D materials, transition metal dichalcogenides (TMDs) and several elemental analogues of graphene have drawn considerable attention because of their exotic electronic properties.[5,6,7,8] Recently, as a new member of this family, transition metal carbides (TMCs) have emerged,[9,10,11] which combine the properties of metals and covalent compounds, owing to their good mechanical stability and high electrical and thermal conductivity. We demonstrate for the first time the shape-dependent surface oxidation of 2D Mo2C crystals, where the elongated flakes are preferentially oxidized under ambient conditions when compared with regular ones, showing higher chemical activity.

Results

Conclusion