ORCID

0000-0002-4603-3110

Keywords

Electrochemistry, Electrochemical Modeling, CO2 Reduction Reaction, Hydrogen Evolution Reaction

Abstract

The urgent need to reduce greenhouse gas emissions has spurred intense interest in sustainable technologies that enable both carbon dioxide (CO2) utilization and hydrogen production. This thesis explores these challenges through a combination of electrochemical simulations, surface science, and experimental validation. Central to the study is the electrochemical CO2 reduction reaction (CO2RR), which offers a promising route for converting CO2 into fuels and chemicals using renewable electricity. We begin by addressing the limitations of traditional modeling approaches for electrochemical systems. A hybrid explicit-implicit solvation model (SOLHYBRID) and an electrode potential control algorithm (TPOT) were developed to simulate the electrochemical interface more realistically under constant potential conditions. These tools were applied to investigate the effect of various cations on CO2RR performance on bismuth (Bi) electrodes. Grand-canonical density functional theory (GC-DFT) and ab initio molecular dynamics (AIMD) revealed that non-metallic ammonium-based cations such as CH3NH3 + enhance CO2 adsorption and reduce activation barriers for H* formation, thereby promoting both CO and formate production. These predictions were experimentally confirmed using both H-cell and gas-diffusion electrode (GDE) systems, showing that CH3NH3 + achieves nearly double the current density compared to conventional cations like Na+. Extending this mechanistic insight, the hydrogen evolution reaction (HER) was studied on Au(111) surfaces. Simulations demonstrated that non-metallic cations support not only conventional water dissociation but also novel pathways such as proton shuttling and direct proton donation-mechanisms inaccessible to metallic cations. These pathways reduce the energy barriers for proton transfer, establishing ammonium-based cations as reactive co-catalysts rather than passive spectators.

Beyond electrocatalysis, we investigated thin film nucleation by studying Pb island growth on Ge(111). DFT calculations and LEEM experiments identified a critical coverage of ∼1.33 monolayers at which explosive island nucleation relieves compressive strain in the Pb wetting layer. The findings highlight collective atomic motion that cannot be explained by thermal diffusion alone, offering broader insight into thin film dynamics. Finally, we explored CO2 capture using superbasic phosphines, focusing on the adsorption of P(tmg)3 on Ag(100). DFT and STM analyses revealed asymmetric adsorption geometries and enhanced surface reactivity due to increased charge localization on the phosphorus atom. These findings support the potential of electron-rich phosphines in reversible CO2 capture applications. Together, these studies present a comprehensive framework that integrates first-principles simulation, custom algorithm development, and experimental validation to uncover atomistic mechanisms in CO2 conversion, hydrogen evolution, and surface adsorption. The work informs future design strategies for electrocatalysts, electrolytes, and functional molecular materials aimed at advancing sustainable energy technologies.

Completion Date

2025

Semester

Fall

Committee Chair

Rahman Talat

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Physics

Format

PDF

Identifier

DP0029717

Document Type

Thesis

Campus Location

Orlando (Main) Campus

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