High-throughput characterization of surface oxygen exchange kinetics in combinatorial oxide thin films

Armstrong, Micah

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https://hdl.handle.net/2142/115747 Copy

Description

Title

High-throughput characterization of surface oxygen exchange kinetics in combinatorial oxide thin films

Author(s)

Armstrong, Micah

Issue Date

2022-04-27

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

Perry, Nicola H

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• oxide thin films
• fuel cells

Abstract

The development of more efficient fuel and electrolysis cells depends heavily on the optimization of electrode material properties. As these properties (e.g., surface catalytic activity, ionic conductivity, and electronic conductivity) can exhibit complex and dissimilar dependences on composition, it is necessary to develop methods to expedite the characterization of these materials with respect to composition. These electrodes provide catalytic activity for various half-cell reactions involving gas-phase species, and the kinetics of those reactions significantly influence the efficiency of the host device. In this work, a method leveraging combinatorial oxide thin films to simultaneously analyze the surface oxygen exchange kinetics in a series of transition-metal-substituted strontium titanate compositions is explored. Two-dimensional optical transmission relaxation (2D-OTR) is a spatially resolved extension of an existing one-dimensional technique that correlates time-dependent defect chemistry with variations in intensity of light transmitted through a combinatorial thin film. In this work a new 2D-OTR setup was constructed and applied to test the spatial variance of surface exchange coefficient (k) across combinatorial library films grown by pulsed laser deposition. The method developed for depositing these films worked relatively well, with consistent thickness, a reasonable composition gradient, and defined masked areas. However, the functionality of these films for optical experiments is in question, as they appear to age at a much faster rate than films deposited in a normal manner. This outcome may be due to the longer time spent at high temperature during combinatorial deposition compared to the growth times of homogeneous films. Going forward, it will be necessary to test more films made using the method described in this work, and adjustments may need to be made to address the issue of rapid aging.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Micah Armstrong

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