2D in-Plane Ordered MXene Nanosheets Derived from (Mo2/3Er1/3)2AlC Rare-Earth i-MAX for Energy Storage Applications
Journal Article
·
· ACS Applied Nano Materials
- Fayetteville State University, NC (United States)
- North Carolina A&T State University, Greensboro, NC (United States)
- Savannah River National Laboratory (SRNL), Aiken, SC (United States)
MXenes have become one of the most versatile families of two-dimensional (2D) materials due to their high conductivity, hydrophilicity, and remarkable electrochemical performance. This has stimulated intense efforts to design and synthesize MXenes, including structurally unique in-plane ordered 2D MXenes called i-MXenes. Here, we have synthesized the quaternary rare earth (RE)-based i-MAX phase (Mo2/3Er1/3)2AlC using an arc melting method, and the corresponding 2D i-MXene was then obtained through a LiF/HCl soft etching process. Literature studies have shown that Al and the RE element are etched out during the etching process, leading to the formation of pure vacancy-ordered Mo1.33C 2D i-MXene. However, our investigation reveals that upon exposure to a fluorine solution, the i-MAX phase forms RE fluoride impurities, which are challenging to remove through HCl−DI water washing and persist in the final product, resulting in impure Mo1.33C@Er i-MXene. These results were confirmed by various characterizations such as X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning transmission electron microscopy. Although the Mo1.33C@Er electrode showed a 24-fold increase in specific capacitance compared to its parent i-MAX phase, it still exhibited a high charge-transfer resistance arising from the insulating nature of RE fluoride byproducts, which adversely influence the overall capacitance behavior of the synthesized 2D Mo1.33C@Er i-MXenes. This study contributes to identifying pathways for the preparation of pure 2D i-MXenes from RE-based i-MAX phases and developing improved synthesis methods. With additional process optimization, the 2D i-MXene holds a strong potential for electrochemical energy storage applications. Additionally, the electronic structures of Mo1.33C were theoretically studied using first-principles density functional theory calculations, which revealed that pristine Mo1.33C is metallic, and this metallic nature is preserved even with −O, −F, and mixed functionalization.
- Research Organization:
- Fayetteville State University, NC (United States); North Carolina A&T State University, Greensboro, NC (United States); Savannah River National Laboratory (SRNL), Aiken, SC (United States)
- Sponsoring Organization:
- Basic Energy Sciences; USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- 89303321CEM000080; SC0024611
- OSTI ID:
- 3013814
- Alternate ID(s):
- OSTI ID: 3012910
- Journal Information:
- ACS Applied Nano Materials, Journal Name: ACS Applied Nano Materials Journal Issue: 2 Vol. 9; ISSN 2574-0970
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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