Date of Completion

11-13-2019

Embargo Period

11-13-2019

Keywords

Reactive spray deposition technology, PGM-free electrocatalyst, Fe-N-C, metal-nitrogen-carbon, oxygen reduction, alkaline electrolyte membrane fuel cell, material characterization

Major Advisor

Radenka Maric

Associate Advisor

Mark Aindow

Associate Advisor

Sina Shahbazmohamadi

Associate Advisor

Jasna Jankovic

Field of Study

Materials Science and Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

The use of expensive platinum-based catalysts has been a major obstacle for the widespread use of low temperature fuel cells. As a result, there is significant commercial and scientific interest in replacing platinum-based electrocatalysts with cost-effective alternatives of comparable performance. This thesis explores the process-structure-property relationship of platinum group metal-free (PGM-free), metal-nitrogen-doped carbon (M-N-C) electrocatalysts for oxygen reduction synthesized by a flame spray pyrolysis process called Reactive Spray Deposition Technology (RSDT). Metal-Nitrogen-Carbon (M-N-C) type Platinum Group Metal-free (PGM-free) electrocatalyst, synthesized directly from liquid solution precursors by the partial combustion of organic material in the RSDT flame. Central to this work is the modification of the RSDT for carbon synthesis using liquid aromatic hydrocarbon-based precursors. The direct synthesis of the M-N-C electrocatalysts using an open atmosphere flame spray pyrolysis technique, has not been reported previously and offers a scalable alternative to the energy-intensive, multi-step furnace-based processes that are conventionally used for synthesizing M-N-C catalysts. The physical and chemical characteristics of the synthesized material are examined and the performance of the catalyst with respect to RSDT process parameters such as precursor composition and fuel equivalence ratio are analyzed with an aim of preparing the groundwork for further development of the synthesis process. The baseline Fe-N-C catalyst synthesized by RSDT exhibits activity towards oxygen reduction in alkaline media and shows excellent dynamic stability even after 4000 potential cycles. Based on these results, additional efforts needed to optimize the RSDT process parameters to improve catalyst activity and for mass-producing M-N-C electrodes are also discussed. As a second subject, this thesis also investigates an application of multi-scale correlative characterization in quality control of carbon black for fuel cell and battery applications. A workflow using correlative characterization techniques including X-CT, laser-milling and elemental analysis is described. Potential failure modes are discussed based on the properties of the impurities analyzed and a case is made for the use of correlative characterization for establishing standards of quality control in commercially produced fuel cell and battery components.

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