Date of Completion

7-12-2020

Embargo Period

7-12-2021

Keywords

mesoporous materials, metal oxides, strong metal-support interactions, catalysis, supercapacitors

Major Advisor

Jie He

Associate Advisor

Steven L. Suib

Associate Advisor

Jing Zhao

Field of Study

Chemistry

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Mesoporous materials process many unique properties, such as high surface area and large pore volume, which are important in the applications of catalysis and energy storage. In these applications, mesoporous materials with controllable porosity and crystallinity are critical. However, the synthesis of mesoporous materials with crystallinity is challenging using traditional methods due to the disruption of mesoporosity at high temperatures. Therefore, a novel synthetic strategy is needed. In this thesis, the design and general synthesis of mesoporous materials with controllable mesoporosity and crystallinity were reported. The mesoporous materials include oxides, sulfides, and metal oxides-based hybrid materials. Furthermore, their porosity-correlated properties and applications in catalysis and energy storage devices are discussed in each chapter.

The first chapter involves the synthesis of mesoporous complex oxides with high crystallinity by colloidal-amphiphile-micelle (CAM) templates. Organosilane-containing CAM templates can convert into thermally stable silica that prevents the overgrowth of crystalline grains and the collapse of the mesoporosity of oxides at high temperatures. This method is general and applicable to various complex oxides with mesoporosity and crystallinity. Furthermore, the antiferromagnetic ordering temperature of mesoporous cobalt titanate is studied to understand the correlation between mesoscale porosity and electromagnetic properties.

Following that, the thermally stable titania confined metal nanoparticles (Au, Pd, and PdAu) are designed and synthesized by the co-assembly of polymer-tethered metal nanoparticles and CAM templates. On one hand, the high-temperature synthesis of mesoporous Au and TiO2 hybrids has been developed. Well-defined nanostructures of Au and porous structures of TiO2 can be retained while improving the crystallinity of TiO2 and its strong metal-support interactions (SMSIs). Under thermal annealing, oxidative SMSIs found in Au-TiO2 show great impact on their photocatalytic activity. On the other hand, using bimetallic PdAu, the impact of oxide support has been studied in term of their hydrogenation activity and selectivity.

The last chapter describes the synthesis of mesoporous metal sulfides through a facile solid-state synthesis. Metal sulfides, such as cobalt sulfides, nickel sulfides, and their binary sulfides, are synthesized. The sulfides are used as electrode materials in supercapacitors. The mesoporosity and the synergistic effect of binary sulfides show great impact on the supercapacitive performance.

Available for download on Monday, July 12, 2021

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