Synthesis of Coinage Metal Nanoparticles As Co Catalysts for Tio2 Based Photocatalysts

Abstract

The work presented in this thesis enlightens the importance of coinage metal nanoparticles (NPs) as co-catalysts for the enhancement of TiO2 photocatalysis. Main emphasis has been given on synthesis of various shapes and sizes of coinage metal nanostructures such as rods, spheres, truncated triangles, wires, etc., and their implication as co-catalyst towards the improvement in the heterogeneous photocatalytic systems, which cannot be achieved through simple conventional approach. This whole work has been divided into eight chapters: Chapter 1: Introduction and Characterization Techniques The first chapter provides the brief introduction on the role of coinage metal nanoparticle as co-catalysts for the improvement of TiO2 photocatalytic reactions. Specific attention has been paid to the impact of catalyst-co-catalyst structure-activity interactions for enhancing the photocatalytic rate. A brief description of various techniques used for the characterization of optical, electrokinetic, co-catalytic and catalytic properties of metallic nanostructures and metal-TiO2 composites has also been incorporated. Chapter 2: Size and Shape Dependent Attachments of Au Nanostructures to TiO2 for Optimum Reactivity of Au-TiO2 Photocatalysis This chapter demonstrates the effects of AuNPs of various sizes and shapes on its co-catalytic activity imparted to TiO2 during photocatalytic oxidation of salicylic acid. The TiO2 photoactivity is remarkably improved with the decreasing size (9.5 ± 0.06 to 3.5 ± 0.25 nm) and increasing the surface to volume (S/V) ratio (0.629 to 1.95 nm-1) of spherical Au co-catalysts loading. The Au nanorod (aspect ratio = 2.8 ± 0.12 and S/V = 0.54 nm-1) attachment to TiO2 significantly decreased the photoactivity compared with the highly active quantum size (3.5 ± 0.25 nm) Au co-catalysts loading. The interaction of AuNPs of various morphologies with TiO2 induces the photoexcited charge transfer process in varied extent, leading to diverse photocatalytic activity.