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Edge Segregated Polymorphism in 2D Molybdenum Carbide
Author(s) -
Zhao Xiaoxu,
Sun Weiwei,
Geng Dechao,
Fu Wei,
Dan Jiadong,
Xie Yu,
Kent Paul R. C.,
Zhou Wu,
Pennycook Stephen J.,
Loh Kian Ping
Publication year - 2019
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201808343
Subject(s) - materials science , molybdenum , carbide , copper , density functional theory , diffusion , catalysis , crystallography , diffusion barrier , polymorphism (computer science) , crystal (programming language) , nanotechnology , layer (electronics) , computational chemistry , metallurgy , thermodynamics , chemistry , organic chemistry , biochemistry , physics , gene , genotype , computer science , programming language
Molybdenum carbide (Mo 2 C), a class of unterminated MXene, is endowed with rich polymorph chemistry, but the growth conditions of the various polymorphs are not understood. Other than the most commonly observed T ‐phase Mo 2 C, little is known about other phases. Here, Mo 2 C crystals are successfully grown consisting of mixed polymorphs and polytypes via a diffusion‐mediated mechanism, using liquid copper as the diffusion barrier between the elemental precursors of Mo and C. By controlling the thickness of the copper diffusion barrier layer, the crystal growth can be controlled between a highly uniform AA ‐stacked T ‐phase Mo 2 C and a “wedding cake” like Mo 2 C crystal with spatially delineated zone in which the Bernal‐ stacked Mo 2 C predominate. The atomic structures, as well as the transformations between distinct stackings, are simulated and analyzed using density functional theory (DFT)‐based calculations. Bernal ‐stacked Mo 2 C has a d band closer to the Fermi energy, leading to a promising performance in catalysis as verified in hydrogen evolution reaction (HER).