Design of Nanostructured Materials Systems for Selective Heterogeneous Catalytic Applications
The development of materials science and engineering in the past decades has been closely related to the emerging challenges associated with industrial and socio-economical requirements. Catalysis research has always been in a very central position in many different industry sectors. Learning from nature, materials research community has been long understood that the isolated catalytic components are no longer sufficient to meet new technological challenges. With more strict requirements of higher conversion and higher selectivity towards specific product(s), and lower energy demands during reactions, it is often very little room for singular catalyst material to play an efficient role. Instead, considerable attention has been placed in composite catalyst research. Rich knowledge in such regard has been obtained in plenty of catalysis research disciplines, like artificial photosynthesis, electrochemical energy conversion, tandem catalysis, as well as new types of conventional nanocatalysts with tentative compositions. Still, large gap in regard of nanocomposite catalyst materials is still difficult to be filled in near future. For instance, materials selection is an open field with uncountable possibilities, opportunities as well as problems. Synergetic effect is the utmost goal while its implementation is still questionable in most systems. Tandem catalysis represents revolutionary catalytic design philosophy, but its application in real life industry reactions is rare so far.
This dissertation depicts mainly the nanocomposite catalyst materials, and studies the synergetic effect between each component in different systems. It is divided into three fields. Firstly, in Part I, 2D material support in catalysis is studied and the influence of supporting material in catalytic activity and selectivity is discussed. It includes Chapter 3, in which graphene-hemin nanocomposite system was developed and explored through a simple wet synthesis route. It is applied in toluene oxidation reaction to examine the effect in primary C-H bond activation reaction. Also, the effect of graphene as support is investigated in detail. Secondly, in Part II, alloy nanocatalysts are designed and the synergetic effect between different components are studied. It includes Chapter 4 and 5. In Chapter 4, nanoporous palladium (Pd) catalyst is synthesized. It is then alloyed with gold (Au) component to form Au-Pd alloy catalyst, with maintained nanoporous morphology. Its superior oxidative catalytic efficiency is assessed in benzyl alcohol oxidation reaction and methanol electro-oxidation reaction. The alloy formation and the synergetic effect between Au and Pd components are studied. In Chapter 5, a nano-star shaped Au-Cu alloy catalyst is synthesized and used in CO2 reduction application. The high hydrocarbon yield is related to the alloy composition and rough surface morphology. Lastly, nanocomposite is widely used in photocatalysis, therefore the contribution of metallic and semiconductor components, and their integration effect is studied. It includes Chapter 6. In Chapter 6, tandem catalyst composed of TiO2 and Au/Pd nanowheel is fabricated. After annealing in inert environment, the nanocomposite is tested in benzimidazole synthesis reaction. It features a highly green reaction route with photocatalytic nature, and of remarkable yield in target molecule product. The role of each component and the synergetic effect is compared.