Role of the surface effect on the structural, electronic and mechanical properties of the carbide MXenes

¹ Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences - Ningbo, Zhejiang 315201, PRC
² Laboratory of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Dalian, Liaoning 116023, PRC
³ State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences P.O. Box 165, Taiyuan, Shanxi 030001, PRC
⁴ Synfuels China - 100195 PRC

^(a) dushiyu@nimte.ac.cn (corresponding author)

Received: 11 June 2015
Accepted: 20 July 2015

Abstract

The two-dimensional material MXene has recently attracted interest for its excellent performance in diverse perspectives. Etched from the parental MAX phase with hydrofluoric acid, the synthesized MXene surface is normally functionalized by oxygen (-O), fluorine (-F) or hydroxyl (-OH) groups. Herein, using first-principles density functional calculations, we investigate the structural, mechanical and electronic properties of the carbide MXene M₂CT₂ (M=Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W; T=-O, -F, -OH). Both the M atom and the surface group T have a significant effect on the MXenes properties. Generally, oxygen functionalized MXenes present smaller lattice parameters and stronger mechanical strength compared to those functionalized by fluorine and hydroxyl groups. exhibits the smallest interlayer thickness and shows the strongest mechanical strength. In regard to electronic properties, five oxygen functionalized members M₂CO₂ (M=Sc, Ti, Zr, Hf, W), two fluorine functionalized members M₂CF₂ (M=Sc, Mo), and hydroxyl functionalized Sc₂C(OH)₂ present semiconducting characteristics, but only Sc₂C(OH)₂ exhibits a direct band gap.