Abstract
Alloying is a long-established strategy to tailor properties of metals for specific applications, thus retaining or enhancing the principal elemental characteristics while offering additional functionality from the added elements. We propose a similar approach to the control of properties of two-dimensional transition metal carbides known as MXenes. MXenes (Mn+1Xn) have two sites for compositional variation: elemental substitution on both the metal (M) and carbon/nitrogen (X) sites presents promising routes for tailoring the chemical, optical, electronic, or mechanical properties of MXenes. Herein, we systematically investigated three interrelated binary solid-solution MXene systems based on Ti, Nb, and/or V at the M-site in a M2XTx structure (Ti2-yNbyCTx, Ti2-yVyCTx, and V2-yNbyCTx, where Tx stands for surface terminations) showing the evolution of electronic and optical properties as a function of composition. All three MXene systems show unlimited solubility and random distribution of metal elements in the metal sublattice. Optically, the MXene systems are tailorable in a nonlinear fashion, with absorption peaks from ultraviolet to near-infrared wavelength. The macroscopic electrical conductivity of solid solution MXenes can be controllably varied over 3 orders of magnitude at room temperature and 6 orders of magnitude from 10 to 300 K. This work greatly increases the number of nonstoichiometric MXenes reported to date and opens avenues for controlling physical properties of different MXenes with a limitless number of compositions possible through M-site solid solutions.
| Original language | English |
|---|---|
| Pages (from-to) | 19110-19118 |
| Number of pages | 9 |
| Journal | Journal of the American Chemical Society |
| Volume | 142 |
| Issue number | 45 |
| DOIs | |
| State | Published - Nov 11 2020 |
| Externally published | Yes |
Funding
Synthesis and experimental characterization of MXenes was supported by the U.S. Department of Energy (DoE), Office of Science, Office of Basic Energy Sciences, grant #DESC0018618. We gratefully acknowledge Dr. John William Freeland for assistance with XAS measurements, which were performed at beamline 4-ID-C at the Advanced Photon Source. This research used resources of the Advanced Photon Source, a U.S. DoE Office of Science User Facility operated for the DoE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. V.B.S. acknowledges support from the U.S. National Science Foundation, grants EFMA-542879 and CMMI-1727717, and the Army Research Office by contract W911NF-16-1-0447 for DFT calculations. N.C.F. was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program. A.C.F. and E.A.S. would like to acknowledge the Vagelos Institute for Energy Science and Technology at the University of Pennsylvania for a graduate fellowship. This work was performed in part at the Singh Center for Nanotechnology at the University of Pennsylvania, a member of the National Nanotechnology Coordinated Infrastructure (NNCI) network, which is supported by the National Science Foundation (Grant NNCI-1542153) and to the Nanoscale Characterization Facility, supported by in part through the University of Pennsylvania Materials Research Science and Engineering Center (MRSEC) (DMR-1720530). XRD, XPS, and SEM-EDS analyses were performed using instruments in the Materials Characterization Core at Drexel University. We thank Dr. Narendra Kurra for the help with collecting Raman spectra and Dr. Mikhail Shekhirev for the assistance with UV–vis spectroscopy measurements.