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Study of Ion Transport from the Two-Dimensional Structure of MXene

Hashemifar, Fatemeh | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55148 (04)
  4. University: Sharif University of Technolog
  5. Department: Physics
  6. Advisor(s): Esfandiar, Ali
  7. Abstract:
  8. Reverse electrodialysis-based membranes are one of the most promising approaches to osmotic energy production. However, conventional reverse electrodialysis membranes have high strength and insufficient mass transfer, which leads to low power density and efficiency. In recent decades, the transport of ions at the nanoscale for the manufacture of reverse electrodialysis machines has attracted much attention. Compared to conventional devices, power density and energy conversion efficiency increase dramatically due to space constraints and electrostatic interactions at the nanoscale. Lamellar nanostructures, which can be easily fabricated by stacking two-dimensional nanosheets, may be a promising and scalable alternative to efficient membranes with phenomena such as fast water transport and high ion selectivity. MXene nanosheets with high mechanical strength and stability in aqueous environments are suitable for creating transmembrane nanochannels. MXene colloidal solution also has liquid crystal property, and its sheets can be adjusted in a specific direction by applying shear. The alignment of the nanosheets in the membrane significantly reduces the membrane's resistance and results in the super-fast transport of water molecules and ions through the membrane. But to date, due to some technical problems such as lack of scalability and difficult coagulation of MXene in the coagulation bath, the use of additive-free MXene fiber as a membrane has not been successful. In this study, we introduce two-dimensional nanoscale channels that can be used in the study of nanofluids and the production of osmotic energy by changing the surface charge density of Mxene nanosheets and fabricating Mxene fibers by wet spinning. Improving the spinning conditions of Mxene fibers leads to a denser structure and reduces the height of nanocanals, thereby increasing ion selectivity. Also, the surface charge density of nanocanals leads to the formation of an electric double layer in the channel and greater selectivity of ions due to electrostatic interactions. High ion selectivity of Mxene fibers with opposite charges can increase the power of electro-dialysis cells made in river water gradient (0.01 M sodium chloride) and seawater (0.5 M sodium chloride) to 12.3 W/m2, which is very More than commercialization power (5 W/m2), as record of generated power to date by membranes. In addition, by arrays of 10 cells and making a reverse electro-dialysis machine, we achieved a voltage of 1.7 V, which can directly process a large number of electronic devices. High scalability and stability suggest Mxene fiber-based membranes as a suitable alternative to clean and sustainable energy production.
  9. Keywords:
  10. Membranes ; Ion Transport ; Nanofluid ; Osmotic Energy Conversion ; Ion Conduction ; Two Dimensional Channels ; MXene Nanosheets

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