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Author ORCID Identifier

https://orcid.org/0000-0001-5944-4114

Date Available

4-30-2027

Year of Publication

2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Arts and Sciences

Department/School/Program

Chemistry

Faculty

Doo Young Kim

Abstract

The development of efficient, durable, and low-cost electrocatalysts is essential for advancing fuel cell, water-splitting technologies, and metal-air batteries. Platinum- and iridium-based catalysts exhibit excellent performance for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively, which are key half reactions in these electrochemical processes. However, the high cost and scarcity of these precious metals drive the search for earth-abundant alternatives.

This dissertation explores transition metal-based electrocatalysts for ORR and OER, with a focus on the design of single atom catalysts, structure-activity relationships, and the use of in situ spectroscopic techniques to investigate electrocatalytic processes and catalyst surface reconstruction. This work focuses on: (1) the synthesis of single atom catalysts (M-N-C) by template-free pyrolysis and zinc-imidazolate framework (ZIF), and (2) the in situ Raman investigation of intermediate species binding and catalyst structural evolution under electrochemical operating conditions.

First, a simple strategy is developed to synthesize copper single-atom catalysts (Cu-SACs) with ultrahigh metal loading using carbon nanodots as metal-capturing precursors. The resulting catalyst achieves up to 20 wt.% atomically dispersed Cu, predominantly as Cu⁺–N₂ sites and exhibits ORR activity comparable to commercial Pt/C in alkaline media. However, durability is limited by Cu demetallation and aggregation, highlighting the need for improved active-site stabilization.

Second, the effect of iron precursor concentration on ZIF-8-derived Fe–N–C catalysts is systematically investigated to establish the relationship between synthesis parameter, catalyst structure and ORR performance. Optimizing the Fe precursor–to–ZIF-8 ratio modulates the porosity, active-site density, and the electronic environment of Fe and N species, thereby directly influencing ORR activity and stability in both acidic and alkaline media. In situ Raman spectroscopy and temperature-programmed desorption are further employed to probe the relationship between catalyst active sites and electrochemical performance.

Finally, composition-dependent surface reconstruction in nickel sulfoselenides (Ni3SxSe2-x), where (x= 0 - 2), during OER is examined using in situ Raman spectroscopy. Sulfur-rich compositions promote the formation of highly active γ-like NiOOH phases, while selenium-rich compositions favor less active β-like phases. An S-rich composition with minor Se incorporation exhibits the best OER performance, demonstrating a synergistic balance between catalytic activity and conductivity.

Overall, this work provides fundamental insights into the design, synthesis and structural evolution of transition metal-based electrocatalysts. By combining rational catalyst design with in situ spectroscopic characterization, this dissertation advances the understanding of structure–performance relationships and advancing the development of efficient and sustainable energy conversion technologies.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2026.459

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Funding Information

  1. The National Science Foundation under grant No. OIA-2327349. Partial salary support was provided by the University of Kentucky Materials Science Research Priority Area (m-RPA) program and by the U.S. Department of Energy under award number DE-SC0022315 (AT, BSG).

  2. Part of this dissertation work is based upon work supported by the U.S. Department of Energy, Office of Electricity (OE), Energy Storage Division. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the US Department of Energy's National Nuclear Security Administration under Contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the US Department of Energy or the United States Government. This article has been authored by an employee of National Technology & Engineering Solutions of Sandia, LLC under Contract No. DE-NA0003525 with the U.S. Department of Energy (DOE). The employee owns all right, title and interest in and to the article and is solely responsible for its contents. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this article or allow others to do so, for United States Government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan.

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