Date of Award
Master of Science
Wenyu . Huang
Layered double hydroxide (LDH) is an inorganic solid with a brucite-like structure that is similar to hydrotalcite, which contains two main metal plates and an anion interlayer in between them. The main metal plates contain both trivalent and divalent metal cations that result in positively charged metal plates. The anion interlayer can compensate for the positive charge on metal plates and result in a natural LDH solid. Their high tunability of chemical composition ordered and uniform metal cation dispersion, and well-distributed layered architecture allows them to become a potential source of intermetallic compound’s (IMC) precursor. Layered double hydroxide can be converted to the mixed metal oxide film (layered double oxide, LDO) after high-temperature calcination, which has a large specific surface area and is more thermally stable. The layered double oxide materials that have specific stoichiometry and homogeneity of composition have been applied directly as catalysts or as catalyst supports.
Intermetallic compounds are well-known for their particular electronic structures and geometries, which show high activity and selectivity towards various types of heterogeneous catalysis reactions as compared with alloys. Non-precious metal IMCs derived from LDH
precursors have attracted research attention because they are low-cost, readily available, and could exhibit meritorious catalytic performance. The synthesizing process of LDH precursors does not involve any toxic organic reagent. Therefore, it is more environmentally friendly than colloidal chemical synthesis methods.
We use LDH as a precursor for two research projects. For the first project, we synthesized the single-atomic Pd which immobilized on the Fe3GaMg7 layered double oxide. Single-atom
catalysts have attracted significant research interest because of their extremely excellent catalytic efficiency and superior selectivity. The Pd/ Fe3GaMg7 catalyst demonstrates promising activity for the Suzuki coupling reaction of bromobenzene and phenylboronic acid at room temperature （Turn over Frequency = 2312h-1). This catalyst has been recycled five times without a significant loss of catalytic activity. It also indicates high tolerance towards a broad scope of the functional groups on the aryl halogen compounds.
For the second project, we synthesized Ni-Ga, Co-In, and Fe-Ga LDH precursors with various metal compositions and generated the corresponding IMCs via the high-temperature reduction in the gas phase.
Luan, Xuechen, "Layered double hydroxide-derived nanomaterials for Suzuki−Miyaura cross-coupling reaction" (2019). Graduate Theses and Dissertations. 17735.
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