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Synthesis and Study of Application of MXene (Ti3C2) Layered Materials in Supercapacitors

Darmiani, Narges | 2023

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 56640 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Iraji Zad, Azam; Esfandiar, Ali
  7. Abstract:
  8. In recent years, MXenes, a class of 2D materials, have drawn significant interest because of their special properties and layered structures. Among the MXenes family, Ti3C2 is a promising candidate in energy storage field due to its unique electrical conductivity, hydrophilicity, surface redox reactions, excellent packing density and high volumetric capacitance. In this thesis, synthesis and supercapacitor application of Ti3C2 have been investigated. HCl and LiF solution and mild exfoliation method has been used for etching Al layers from Ti3AlC2 and MXene synthesis. To analyze the structure of this material, scanning electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and zeta potential test have been used. The electrochemical performance of the electrodes was evaluated by cyclic voltammetry, galvanic charge/discharge and electrochemical impedance spectroscopy. For preparation of the electrodes, Ti3C2 was used to bridge electroactive materials with substrate. First, Ti3C2 was coated on a Cu wire and a porous cauliflower-like Ni film was deposited on it through a hydrogen bubble template approach. Eventually, this structure was used for growth of the Ni(OH)2 nanostructure. The porous cauliflower-like morphology provided high surface area, short ion penetration path and low contact resistance between electroactive material and wire. The electrodes delivered high specific capacitances of 1725.23 Fcm-3 and 19.81 Fcm-2. Moreover, the fabricated flexible asymmetric fiber-shaped supercapacitor based on Ni(OH)2-Ni-Ti3C2@CW and Ti3C2 delivered a maximum energy density of 206 μWhcm-2 at a power density of 1.94 mWcm-2 and showed good mechanical and cyclic stability with capacitance retention of 89.3% after 7000 cycles. In the next step, MXene fibers were prepared by wet-spinning method. The relative compact structure of fibers guarantees good electrical and mechanical properties, but in another side hinders ion diffusion and corresponding capacitance. Therefore, we tried to minimize the trade-off between these properties. For this purpose, the bath rotation speed, coagulation temperature and coagulant ions have been investigated. The fiber-shaped freestanding electrodes delivered a high volumetric capacitance of 1802.24 F cm-3 and excellent rate capability. These electrodes also retained 97.70% of the initial capacitance after 5000 cycles. This good performance can be ascribed to ordered and porous dense structure of the fibers as well as high their electrical conductivity and surface redox reactions of the MXene. Then, the symmetric supercapacitors were fabricated by these fibers. The supercapacitor exhibited a maximum energy density of 44.90 mWhcm-3 at a power density of 7686.90 mW cm-3. It also demonstrated remarkable cyclic stability with a capacitance retention of 98.30% after 5000 cycles and good mechanical performance with a capacitance retention of 98.80% after 200 bending cycles
  9. Keywords:
  10. Supercapacitor ; Titanium Carbide Mxene Composite ; Titanium Carbide ; Fiber Shaped Supercapacitors ; MXene Fibers

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