Synthesis and Characterization of Nanostructure Materials as Catalysts for Environmental and Energy Storage Applications

Environmental pollution and energy depletion are the two major issues we human beings have faced for the 21st century and even beyond. The bloom of nanotechnologies has brought new hope for solving these issues, along with the progress being made in engineering and information technologies. The work in this thesis only represents one piece of science like many others. Herein, the creation of novel materials and their screening as promising functionalized catalysts, targeting applications for example, in volatile organic compounds(VOC) abatement, heterogeneous oxidation, and solar energy driven water splitting towards H2 production as a substituting fuel for fossil fuel are sought. In the end, a novel nickel doped manganese oxide/graphene oxide composite was presented as a superior anode material for lithium ion batteries by achieving large capacities, good rate capabilities, and cycling stabilities. For environmental applications, a novel material, manganese-containing MFI type Mn-ZSM-5 zeolite was synthesized by a facile one-step hydrothermal method using tetrapropylammonium hydroxide (TPAOH) and manganese (III)-acetylacetonate as organic template and manganese salts, respectively. Direct evidence of the incorporation of Mn in the zeolite framework sites was observed by performing structural parameter refinements, and supported by data collected from other characterization techniques such as: IR, Raman, UV-Vis, TGA, N2-adsorption, SEM, TEM, EDX, and XPS. The unique optical properties of Mn-ZSM-5 from UV-vis spectra show two absorption peaks at 250 nm and 500 nm. The unique absorption was interpreted by studying photophysical properties of a model Mn(O-SiH3)4- compound, an Mn-embedded zeolite cluster, and model Mn oxides utilizing Time-Dependent Density Functional Theory (TD-DFT). The catalytic activity was studied in both gas phase benzyl alcohol oxidation and toluene oxidation reactions with remarkable oxidative activity presented for the first time. These reactions result in a 55 % yield of benzaldehyde, and 65 % total conversion of toluene to carbon dioxide for the 2% Mn-ZSM-5. Severe climate changes and depleting fossil fuel supplies call for sustainable energy conversion systems and storage techniques. The storage of solar energy by formation of fuel molecules, i.e. H2 and methanol provides a viable way to replace our current reliance on fossil fuels. In all these solar fuel productions, a large amount of protons and electrons are needed as the fuel sources and reducing equivalents, respectively. Water, as an inexpensive and abundant source can produce protons and electrons after being oxidized. Consequently, water oxidation (WO) has received extensive research efforts which mainly focus on development of accessible catalysts to drive WO at low overpotentials. In this regard, manganese has a leading role in catalyzing water oxidation efficiently with many unmatchable merits: low toxicity, high availability, and low cost. More importantly, manganese is Nature’s choice as catalyst for producing oxygen via the photosynthesis system II (PSII). Our study over a variety of manganese oxide structures and their catalytic activities in the oxygen evolution reaction (OER) showed an order of activity was followed: α-MnO2\u3e AMO \u3e β-MnO2 \u3e δ-MnO2, which has uncovered a clearly structure-property relationship of MnO2 in catalyzing OER