Elemental and structural behaviors of bimetallic nanoparticles under reactive environments and its implication in catalyst design, processing, and performance

Bimetallic nanocatalyst;Environmental transmission electron microscopy (ETEM);Core-shell nanoparticle;Adsorbate induced restructuring;Intermetallic;Heterogeneous catalysis

Pan, Yung-Tin

关键词: Bimetallic nanocatalyst;    Environmental transmission electron microscopy (ETEM);    Core-shell nanoparticle;    Adsorbate induced restructuring;    Intermetallic;    Heterogeneous catalysis;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/97539/PAN-DISSERTATION-2017.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Bimetallic nanocatalyst often shows enhanced performance where the key lies not only on the overall composition but more importantly, is related to the specific atomic arrangement of the two metal elements on the and near surface regions. In order to make the most out of bimetallic nanocatalyst, it is important to understand how to control its near surface elemental arrangement as well as how it behaves under the complex reaction environments. In this dissertation, the structural and elemental rearrangements of various bimetallic nanocatlyst were studied focusing on the processing and identifying the structure of a working catalyst. The first part emphasizes on how post-synthesis thermal process of bimetallic nanocatlyst for improved catalytic performance, which includes the thermally driven composition redistribution of Pt-Ni octahedral oxygen reduction reaction (ORR) nanocatalyst, the formation of Ag-Pt compositional intermetallics from alloy nanoparticles for formic acid oxidation (FAOR), and the regioselective atomic rearrangement of Ag-Pt octahedral catalysts by chemical vapor-assisted treatment. The second part is dedicated to identifying the actual structures of the bimetallic nanocatalysts under reaction conditions and how it affects performance, with more emphasis on product selectivity. The two model systems are metal-on-metal Rh-on-Pd for CO2 hydrogenation and Cu@CuAg nanocatalyst for propylene epoxidation.Environmental transmission electron microscopy was utilized in most of the projects mentioned above and provided critical information with high spatial resolution in realtime.The in situ microscopic observations shows good correlation with ex situ microscoscopic, surface sensitive spectroscopic, electrochemical, and chromotagraphic analysis as well as density functional theory (DFT) calculations.The discovery in this dissertation indicates how the multiple governing factors determines the restructuring of different bimetallic nanocatalyst under various reactive thermal-chemical environments. It provides insights not just in the synthesis and processing of bimetallic nanocatalysts but also on the design of reaction conditions for the optimum working structure that leads to the best performance.