Development of complex metal oxide electrocatalysts for oxygen evolution reaction

Zhang, Cheng

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https://hdl.handle.net/2142/115723 Copy

Description

Title

Development of complex metal oxide electrocatalysts for oxygen evolution reaction

Author(s)

Zhang, Cheng

Issue Date

2022-04-20

Director of Research (if dissertation) or Advisor (if thesis)

Yang, Hong

Doctoral Committee Chair(s)

Yang, Hong

Committee Member(s)

• Kenis, Paul J. A.
• Zuo, Jian-Min
• Su, Xiao

Department of Study

Chemical & Biomolecular Engr

Discipline

Chemical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• electrocatalysis
• complex metal oxide
• oxygen evolution reaction

Abstract

Generating green hydrogen with water electrolysis is regarded as a promising solution to the climate and energy crisis. The major challenge of water splitting is to develop efficient electrocatalysts for oxygen evolution reaction (OER) with high activity, stability and low cost. But the lack of fundamental understanding in the OER mechanism limits the application of this technique at an industrial level. This dissertation focuses on: (1) Developing efficient OER electrocatalysts with different crystal structures; (2) Regulating the properties of catalysts by metal substitution or varying synthetic conditions to determine the dominated impacting factors on OER performance; (3) Developing novel characterization techniques to better understand the reaction mechanism of OER. Chapter 2 focuses on a Mn substituted pyrochlore Y2[MnxRu1-x]2O7 which exhibited an enhanced performance compared to reference catalysts RuO2 and Y2Ru2O7. The dominated impacting factor was determined to be the oxidation state of Ru. Chapter 3 presents a series of pyrochlore Ln2Ru2O7 with lanthanide metals as A-site metals. Ru-O bond length was found to be a descriptor for the OER performance. Secondary-ion mass spectrometry (SIMS) was applied to these catalysts, and a correlation between the metal-oxygen group and OER performance was discovered. Based on these results, an A-site synergy lattice oxygen mechanism was proposed for the first time. Chapter 4 shows the work about mixed B-site Ruddlesden-Popper Sr2(RuxIr1−x)O4¬, which shows high OER activity in acidic media, attributed to the high concentration of hydroxyl groups on the surface of the electrocatalysts. Chapter 5 is about the temperature dependent phase transition of perovskite SrCo0.9Fe0.1O3. As temperature increases, the crystal structure became amorphous structure, metal oxide, oxygen deficient perovskite and finally perovskite, The OER performance were tested in alkaline system, while the oxygen deficient perovskite shows highest activity, resulting from high ECSA, low impedance and the high concentration of oxygen vacancies. The results in this dissertation provide new insights towards the rational design of efficient OER catalysts and a better understanding of the reaction mechanism.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Cheng Zhang

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