Bimetallic Nanoparticles for Advanced Energy Conversion Technologies

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Sims, Christopher
Eichhorn, Bryan W
The increased demand for a more sustainable energy infrastructure has spurred the development of innovative energy conversion processes and devices, such as the proton exchange membrane fuel cell (PEMFC). PEMFCs are highly regarded as a clean alternative energy technology for various applications, such as motor vehicles or power generators. Factors limiting their commercial viability include the poisoning of the hydrogen oxidation reaction (HOR) electrocatalyst at the anode by carbon monoxide (CO), an impurity in the H2 fuel feedstocks derived from hydrocarbons, and the high expense and inefficiency of the oxygen reduction reaction (ORR) electrocatalyst at the cathode. The research described in this dissertation entails the synthesis and characterization of new bimetallic nanoparticle (NP) catalysts with controlled sizes, compositions, and architectures. By varying the NPs' compositions, structures, and electronic environments, we aimed to elucidate the physical and chemical relationships that govern their ability to catalyze chemical reactions pertinent to PEMFC operation. The ongoing research and development of these NP-based catalytic systems is essential to realizing the viability of this energy conversion technology. We describe the development of a simple method for synthesizing monometallic and bimetallic NPs supported on various reduced graphene oxide (rGO) supports. Electrochemical studies illustrate how the chemical nature of the rGO support impacts the catalytic behavior of the NP catalysts through unique metal-support interactions that differ depending on the elemental composition of the NP substrate. In another study, we present the synthesis and characterization of CoxPty NPs with alloy and intermetallic architectures and describe how their inherent characteristics impact their catalytic activities for electrochemical reactions. CoxPty NPs with alloy architectures were found to have improved CO tolerance compared to their intermetallic counterparts, while the performance of the CoxPty NPs for ORR catalysis was shown to be highly dependent on the NPs' crystal structure. Finally, we present the synthesis and characterization of various bimetallic core-shell NPs. Preliminary data for CO oxidation and PrOx catalysis demonstrated how subsurface metals modify the electronic structure of Ni and enhances its catalytic performance for CO oxidation and the PrOx reaction.