Design of group 10 (Pd, Pt) bimetallic nanoparticles and application toward next generation energy storage

Abstract

Nanoparticles (NPs) have received considerable attention because of their unique magnetic, optical, and electronic properties which are different from the properties in the bulk state. Among the metal NPs, plat-inum group metals (PGMs) have been widely used as catalysts. PGM catalysts are exclusive in regard of ac-tivity and selectivity toward numerous hydrogenation and oxidation reactions, and they exhibit a high stability in extreme reaction conditions. These catalysts are considered as promising candidates for not only synthetic chemistry but also next generation energy storage systems, such as fuel cells and Li-air batteries. However, their practical uses are limited by high cost and scarcity. Recently, many researchers have studied on the improvement of catalytic performance by controlling the composition and morphology of NPs to maximize the activity and strengthen the durability with the reducing of the amount of PGMs. In this study, we desire to synthesize bimetallic catalysts employing either platinum (Pt) or palladium (Pd) metals and apply them to efficient catalysts in fuel cells and Li-air batteries. We have synthesized well-defined Pd-Pt core-shell NPs with controlled shell thickness and employed them for the application toward oxygen reduction reaction (ORR) of polymer-exchange-membrane fuel cells (PEMFCs). In addition, we have prepared PdCu bimetallic NPs with mixed crystalline phase (face-centered cubic (fcc) and B2-type structure), which were employed as catalysts for ORR and oxygen evolution reaction (OER) in Li-air batteries. In chapter 2, we report a designed synthesis of well-defined Pd@Pt core-shell NPs with a controlled Pt shell thickness of 0.4-1.2 nm via a facile wet chemical method and their electrocatalytic performances for ORR as a function of shell-thickness. Pd@Pt NPs with pre-determined structural parameters were prepared via the in situ heteroepitaxial growth of Pt on as-synthesized 6 nm Pd NPs without any sacrificial layers n...