Abstract
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).
Original language | English |
---|---|
Article number | 1808343 |
Journal | Advanced Materials |
Volume | 31 |
Issue number | 15 |
DOIs | |
State | Published - Apr 12 2019 |
Funding
X.Z. and W.S. contributed equally to this work. K.P.L thanks MOE Tier 2 grant “Porous, Conjugated Molecular Framework for Energy Storage” (MOE2016-T2-1-003), National Research Foundation, Prime Minister’s Office. W.Z. acknowledges support from the National Key R&D Program of China (2018YFA0305800) and the Natural Science Foundation of China (51622211). S.J.P. thanks the National University of Singapore for funding and MOE for a Tier 2 grant “Atomic scale understanding and optimization of defects in 2D materials” (MOE2017-T2-2-139). Theoretical calculations (W.S., Y.X., and P.K.) were supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. W.S. acknowledges Dr. Igor Di Marco at Uppsala University to provide the latest version of relativistic spin polarized toolkit (RSPt), an FP-LMTO code, and the computational resources at the National Supercomputing Center in Sweden with project ID SNIC2017-1-374. This manuscript was coauthored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy. gov/downloads/doe-public-access-plan). X.Z. and W.S. contributed equally to this work. K.P.L thanks MOE Tier 2 grant ?Porous, Conjugated Molecular Framework for Energy Storage? (MOE2016-T2-1-003), National Research Foundation, Prime Minister's Office. W.Z. acknowledges support from the National Key R&D Program of China (2018YFA0305800) and the Natural Science Foundation of China (51622211). S.J.P. thanks the National University of Singapore for funding and MOE for a Tier 2 grant ?Atomic scale understanding and optimization of defects in 2D materials? (MOE2017-T2-2-139). Theoretical calculations (W.S., Y.X., and P.K.) were supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. W.S. acknowledges Dr. Igor Di Marco at Uppsala University to provide the latest version of relativistic spin polarized toolkit (RSPt), an FP-LMTO code, and the computational resources at the National Supercomputing Center in Sweden with project ID SNIC2017-1-374. This manuscript was coauthored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
Keywords
- MXene
- molybdenum carbide
- phase engineering
- scanning transmission electron microscopy