Date of Award

Summer 8-15-2025

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Committee Advisor

Sharmila Mukhopadhyay

Second Committee Member

Tomas Marangoni

Third Committee Member

Justin Lapp

Abstract

Electrochemical devices like water electrolyzers and sensors can be significantly improved through the development of advanced electrodes. Key performance factors, such as high interaction area, chemical stability, charge transport, and redox activity are difficult to achieve with a single material. As a result, combining materials to leverage their synergistic properties is often necessary. Common strategies for integrating nanomaterials into electrodes include forming pastes followed by thermal binding, applying nanomaterial-based coatings onto a base structure or commercially available electrodes, electrodeposition of nanoparticles on substrate, dip coating of nanomaterials and so on. While nanomaterials offer advantages like high surface activity and tunable electronic behavior, their integration into practical reusable electrodes is limited by issues like coagulation, poor dispersion of materials, poor integration of structures and full utilization of surface area. To overcome these challenges, this study investigates a hierarchical electrode design in which carbon nanotubes and nanoparticles are covalently bonded to a porous substrate, enhancing conductivity, surface reactivity, and active site availability.

This study investigates the electrochemical behavior of hybrid hierarchical structures composed of multiwalled carbon nanotubes (MWCNTs) grown on reticulated virous carbon (RVC) foams which can be further modified with palladium (Pd) nanoparticles. MWCNTs provide a high surface area and excellent electrical conductivity, while the porous RVC substrate provides a high surface area to facilitate fluid transport in electrochemical electrode. The MWCNTs contribute to high surface area and excellent electrical conductivity, while the porous RVC substrate enhances fluid transport and overall electrode accessibility. The investigation of their performance was achieved using cyclic voltammetry to study their double layer capacitance, using linear sweep voltammetry (LSV) and Tafel analysis these hybrid structures were evaluated for both OER and hydrogen evolution reaction (HER) Incorporating CNTs onto RVC results in a ninefold increase in double layer capacitance, improved OH⁻ adsorption during the oxygen evolution reaction (OER), a reduced Tafel slope in potassium hydroxide (KOH), and an increase in exchange current density from 0.54 μA/mg to 1.54 μA/mg. Further modification with Pd nanoparticles enhances charge transfer dynamics and doubles the capacitance compared to the RVC-CNT structure, indicating a significant increase in active site density. The results demonstrate that extended nanotube growth times and the presence of Pd nanoparticles contribute to improved onset potential, Tafel slopes for water electrolysis, and higher active sites density indicating enhanced electrocatalytic efficiency. The conductive MWCNT network, coupled with the catalytic properties of Pd, facilitates effective charge transfer and improves reaction kinetics.

This study provides insight into some of the underlying mechanisms that contribute to the improved performance of MWCNT-RVC and MWCNT-RVC-Pd hybrid electrodes, with findings suggesting their strong potential for advancing electrochemical applications. Future research will focus on understanding their structure-property relationships and refining growth and deposition parameters to improve their efficiency and investigating broader applications in electrocatalysis and water electrolysis.

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