Dissertation
MXenes: a new family of two-dimensional materials and its application as electrodes for Li-ion batteries
Doctor of Philosophy (Ph.D.), Drexel University
Apr 2014
DOI:
https://doi.org/10.17918/etd-4526
Abstract
Two-dimensional, 2D, materials, such as graphene, possess a unique morphology compared to their 3D counterparts, from which interesting and novel properties arise. Currently, the number of non-oxide materials that have been exfoliated is limited to two fairly small groups, viz. hexagonal, van der Waals bonded structures (e.g. graphene and BN) and layered transition metal chalcogenides. The MAX phases are a well established family of layered ternary transition metal carbides and/or nitrides, with a composition of M_[n+1]AX_n, where M is an early transition metal, A is one of A group elements, X is C and/or N; with n = 1, 2, or 3. The aim of this work is to exfoliate the MAX phases and produce 2D layers of transition metals carbides and/or nitrides by the selective etching of the A layers from the MAX phases. We labeled the resulting 2D M_[n+1]X_n layers "MXenes" to emphasize the loss of the A group element from the MAX phases and the suffix "ene" to emphasize their 2D nature and their similarity to graphene. The etching process was carried out using aqueous hydrofluoric acid at room temperature. Thirteen different MXenes were produced as a result of this work, viz., Ti₂C, Nb₂C, V₂C, Mo₂C, (Ti_[0.5],Nb_[0.5])₂C, (Ti_[0.5],V_[0.5])₂C, Ti₃C₂, (Ti_[0.5],V_[0.5])₃C₂, (V_[0.5],Cr_[0.5])₃C₂, Ti₃CN, Ta₄C₃, Nb₄C₃ and (Nb_[0.5],V_[0.5])₄C₃. The as-synthesized MXenes were terminated with a mixture of OH, O, and/or F groups. Sonicating MXenes resulted in separating the stacked layers to a small extent. When Ti₃C₂ was intercalated with dimethylsulfoxide, however, followed by sonication in water, large-scale delamination occurred, which resulted in aqueous colloidal solutions that could in turn be fabricated into MXene "paper". MXenes were found to be electrically conductive, hydrophilic and stable in aqueous environments, a rare combination indeed, with huge potential in many applications, from energy storage, to sensors to catalysts. This work focused on the use of MXenes as electrode materials in Li-ion batteries. They exhibited excellent capability to handle high cycling rates with good gravimetric capacities. The lithiation and delithiation were found to be due to redox intercalation/deintercalation reactions.
Metrics
389 File views/ downloads
332 Record Views
Details
- Title
- MXenes
- Creators
- Michael Naguib Abdelmalak - DU
- Contributors
- Michel W. Barsoum (Advisor) - Drexel University, Materials Science and EngineeringYury Gogotsi (Advisor) - Drexel University, Materials Science and Engineering
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) (1970-2026); College of Engineering (1970-2026); Drexel University
- Other Identifier
- 4526; 991014632679004721