Abstract

Electrocatalysis plays a central role in the development of renewable energy technologies as it enables direct conversion between renewable electricity and chemical energy. To design efficient electrocatalysts, it is essential to understand the relationship between the structure and the activity of electrocatalytic materials. Scanning electrochemical microscopy (SECM) is a scanning probe technique capable of imaging local electrocatalytic activity under operating conditions, of which the spatial resolution depends on the size and shape of the probe. Compared to commercial SECM probes which have limited resolution capabilities, I have developed novel nanoelectrode probes by etching sharp platinum tips followed by electropolymerization coating of the tip except at the apex, which can greatly reduce the exposed electrode area of the probe to improve the spatial resolution of SECM imaging. These nanoelectrode probes were successfully used to image the activity of single platinum nanoparticles dispersed on a silicon support, thus surpassing the resolution capabilities of the best commercially available probes. This demonstrates the improved ability to reveal the local activity of nanostructured electrocatalysts. In addition, I used conventional electrochemical methods to investigate the structure-activity relationships of nanomaterials for important reactions, including the nitrate reduction reaction and the oxygen evolution reaction (OER). I revealed the effects of ruthenium nanoparticle size and copper oxidation state on the activity and selectivity (Faradaic efficiency) for the electroreduction of nitrate to ammonia on these metal nanoparticle catalysts. I also performed electroanalytic studies of cobalt oxide nanosheets supported on nickel foam, as well as titanium dioxide supported on plain and PTFE-doped carbon paper as electrocatalysts for the OER. In summary, I developed novel nanoelectrode SECM probes for the mapping of electrocatalytic activity of nanomaterials at nanoscale resolutions, and these nanoelectrode probes can be widely used to image local electrocatalytic activity in operando to reveal local structure-activity relationships. I further elucidated the effects of nanoparticle size and oxidation state of metal-based electrocatalysts for nitrate reduction and oxygen evolution, and these new understandings of structure-activity relationships can provide guidance for the rational design of efficient electrocatalysts for efficient electrolyzers and help guide us towards a more sustainable future.

Notes

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Graduation Date

2023

Semester

Spring

Advisor

Feng, Xiaofeng

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Physics

Degree Program

Physics

Format

application/pdf

Identifier

CFE0009581; DP0027598

URL

https://purls.library.ucf.edu/go/DP0027598

Language

English

Release Date

May 2024

Length of Campus-only Access

1 year

Access Status

Doctoral Dissertation (Open Access)

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