Electronic Theses and Dissertations Archive

Date

2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Committee Chair

Okenwa Okoli

Committee Member

Aaron Robinson

Committee Member

Alexander Headley

Committee Member

Natalie Arnett

Committee Member

Ranganathan Gopalakrishnan

Abstract

The global shift toward renewable energy has intensified the demand for efficient energy storage systems. While supercapacitors offer high power density and fast charging, their commercial viability is hindered by low energy density and the poor oxidative stability of high-performance electrode materials. This research focuses on vanadium-based MXenes (V2CTx) and their composites as advanced pseudocapacitive materials to overcome these challenges. The study first optimizes the synthesis of the precursor V2AlC MAX phase using pressureless sintering. It was determined that a sintering temperature of 1300 °C and an aluminum molar ratio of 1.2 yielded a phase purity of 94.38% and a superior electrical conductivity of 7.19E5 S/m. To address the well-known issue of the rapid oxidation of V2CTx in aqueous environments, a significant bottleneck for vanadium MXenes, the second phase of this research introduces L-ascorbic acid sodium salt (NaAsc) as a sustainable antioxidant. Experimental results show that a mass concentration of 200 mg of NaAsc effectively stabilizes the MXenes structure via a localized edge-capping mechanism. This stabilization achieved a specific capacitance of 210.88 F/g and maintained 92% capacity retention over 5,000 cycles. An equivalent circuit model was also developed to accurately describe ion transport, charge transfer resistance, and interfacial processes, providing deeper insight into the electrochemical mechanisms governing performance. Furthermore, the dissertation explores V2CTx/Polyaniline (PANI) composites synthesized through in-situ and ex-situ polymerization. The combined effect of the highly conductive MXene and the redox-active PANI polymer, achieved through in-situ polymerization, enhanced the electrochemical performance. A symmetric coin-cell device was fabricated to demonstrate the practical application of these nanocomposites, showcasing their potential for high-performance, long-term energy storage. Overall, this work advances understanding of vanadium-based MXenes by linking precursor synthesis, surface functionalization, and composite synthesis to electrochemical performance. The findings provide both fundamental insights and practical strategies to improve the stability, energy density, and long-term reliability of MXene-based supercapacitors, thereby contributing to the development of next-generation energy storage systems.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest/Clarivate.

Notes

Embargoed until 2029-04-02

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Available for download on Monday, April 02, 2029

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