ORCID

0000-0003-1372-0210

Keywords

Electrocatalysis, Cation effect, Microenvironment, CO2 reduction

Abstract

Electrocatalysis plays a key role in the development of energy conversion technologies including fuel cells and electrolyzers, enabling a sustainable production of chemicals and fuels when powered by renewable electricity. Beyond the electrocatalytic materials, the local environment around catalytic sites, including liquid electrolyte and gaseous reactant/product, has a significant impact on gas-involving reactions such as CO2 reduction and hydrogen evolution. This dissertation focuses on understanding the effects of electrolyte cations and electrode wettability on the reaction kinetics and bubble dynamics of electrocatalytic reactions. First, I studied the effect of non-metal cations including ammonium and alkylammonium on CO2 reduction with Bi catalyst, which showed a significant improvement of CO production activity compared to that with alkali metal cations, but a minor one on formate production. We found that the cations play a critical role by stabilizing the *CO2 intermediate for CO production, which is however not necessary for formate. Based on the understanding, the cations were utilized to promote CO2 electroreduction on Au with gas-diffusion electrodes, achieving a multi-fold enhancement of the activity. The ammonium-based cations also exhibited a significant promotion of the hydrogen evolution reaction in neutral electrolyte, which is attributed to a proton-shuttling mechanism enabled by the cations with proton-donating abilities. Furthermore, I studied the effect of electrode wettability on gas-evolving electrocatalysis by tuning the wetting properties with O- or F-doped carbon supports to make it more hydrophilic or hydrophobic, which both improved the activity as compared to that with pristine carbon support. Hydrophilicity increases the exposure of catalyst surface to liquid electrolyte, while hydrophobicity accelerates the bubble dynamics of generated N2 and recovery of active sites. Our research provides deep understandings of the effects of electrolyte cations and electrode wettability on electrocatalysis and novel insights for the rational design of efficient electrocatalytic systems for renewable energy applications.

Completion Date

2024

Semester

Fall

Committee Chair

Feng, Xiaofeng

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Physics

Format

Print

Identifier

DP0029706

Document Type

Thesis

Campus Location

Orlando (Main) Campus

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