Determination of reliable minimum, disproof-based particle formation mechanisms: investigation of a second-generation Ir(0)n nanoparticle system
Date
2021
Authors
Whitehead, Christopher Breck, author
Finke, Richard, advisor
Neilson, Jamie, committee member
Van Orden, Alan, committee member
Shipman, Patrick, committee member
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Abstract
A long-sought goal in particle formation is an understanding of the chemical reaction mechanism. The complete understanding of the associated processes (nucleation, growth, and agglomeration) will yield particle size and distribution control. Mechanistic control and knowledge will yield improvements in the development of renewable energy and catalytic materials. The current state of chemical reaction mechanisms and the direct methods to study them are presented in an in-depth literature review in Chapter II. The best, state-of-the-art case studies are examined and the minimum criteria for a reliable, disproof-based chemical mechanism are presented. The experimental work presented in this dissertation centers on a second-generation {[(1,5-COD)IrI•HPO4]2}2– precursor to Ir(0)~150(HPO42–)x nanoparticle system. The exhaustive investigation of the reaction speciation and the dependence of IrI and HPO42– concentrations on the reaction kinetics are presented in Chapter III. Based on the reaction kinetics and there experimentally determined nucleation step, the molecular mechanism of Ir(0)~150(HPO42–)x nanoparticle formation is elucidated. Next, in Chapter IV, the second-generation {[(1,5-COD)IrI•HPO4]2}2– precursor to Ir(0)~150(HPO42–)x nanoparticle system is monitored directly by X-ray absorption spectroscopy and small-angle X-ray scattering and indirectly by in-house cyclohexene reporter reaction, gas-liquid chromatography, proton nuclear magnetic resonance, and transmission electron microscopy. A total of 6 physical methods are used to follow the particle formation kinetics. Finally, mechanism-enabled population balance modeling is applied as a final test of the proposed mechanism.
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Subject
iridium
nanoparticle
disproof-based
nucleation
mechanism