Nanomaterials Engineering and Applications in Catalysis

Catalysis plays an essential role in industrial applications of direct relevance to many aspects in our daily lives, such as petroleum refining, fine chemical and pharmaceutical production, energy conversion and storage, and automotive emissions control. Design and fabrication of highly active catalysts in an efficient and cost-effective way is thus an important topic. This dissertation discusses our efforts in the engineering and applications of nanomaterials, which could be divided into three consecutive stages: (1) synthesis, (2) stabilization, and (3) application in catalysis. In the first stage, by using Ag nanoplates as a model system, we attempt to outline the key components that determine the formation of nanomaterials with desired morphology, clarify the roles of each reagent, provide highly reproducible recipes for synthesis, and therefore take a significant step towards the complete understanding of the mechanism behind the experimental phenomena. Using this understanding, Ag nanoplates with various aspect ratios and widely tunable SPR bands have been successfully obtained. One of the major challenges for the use of nanostructured materials as catalysts is their chemical and structural stability. In the second stage, by embedding nanocatalysts within a mesoporous metal oxide shell, we are able to prepare nanocatalysts with enhanced stability in both gas and aqueous phase reactions. A general strategy, called the "surface-protected etching" process, has been developed as the major synthetic tool for producing mesoporous shells for the stabilization of noble metal nanocatalysts. A sandwich-like structure was further proposed, in which multi-functional materials could be incorporated to make recyclable and highly efficient catalysts. Finally, for practical applications, TiO2-based nanomaterials have been used as the model system to investigate the factors that determine the preparation of efficient photocatalysts. Mesoporous TiO2 photocatalysts with high surface area and high photocatalytic activity have been prepared through a self-assembly approach. Based on our improved understanding of photocatalysts, we have designed and synthesized a highly efficient, stable, and cost-effective TiO2-based photocatalyst by combining both non-metal doping and noble metal decoration. The new photocatalysts show excellent performance in degradation reactions of a number of organic compounds under the irradiation of UV, visible, and direct sunlight