Electrocatalytic and Antibacterial Applications of Sandwich Type Polyoxometalates

Abstract

The primary goal of this dissertation is to study the structure-property relationship of sandwich type polyoxometalates and to employ these versatile molecules in electrocatalytic applications such as oxygen generation and reduction. An attempt has been made to design novel catalysts by a systematic variation of the type of the substituted transition metal in the sandwich type polyoxometalate framework. Chapter 1 presents an introduction to polyoxometalate structure and chemistry with a detailed literature review of the value added properties responsible for the catalytic activities of these POMs. A brief insight into the phenomenon of electrocatalysis is provided and the suitability of employing POMs as electron transfer mediators is discussed in detail.

Chapter 2 is a detailed outline of the synthesis and structural characterization of sandwich type polyoxometalates. The novel transition metal substituted sandwich type polyoxometalates were synthesized and characterized by the following analytical techniques - FTIR, Raman, UV-VIS, elemental analysis and single crystal XRD. In chapter 3, a detailed discussion on the electrochemical properties of sandwich type polyoxometalates was provided along with some preliminary electrocatalytic applications. Chapter 4 deals with the study of electrocatalysis of Ru2POM for oxygen evolution reaction. In-situ detection of oxygen generated at the gold working electrode was performed with Clark oxygen sensor and rotating ring disc electrode studies. A detailed description of the measurement of oxygen concentration is provided. Chapter 5 presents the application of electrochemical surface Plasmon resonance spectroscopy in studying the adsorption of sandwich type POMs onto gold electrodes as an elegant complementary technique to electrochemical quartz crystal microbalance method (EQCM) to probe the interfacial processes. Chapter 6 represents the successful application of transition metal substituted polyoxometalates as co-catalysts for oxygen reduction reaction at several noble metal electrodes, such as gold, palladium and platinum. A simple thermodynamic model has been propounded as the basis for the choice of bimetallic catalysis. Chapter 7 deals with the application of sandwich type polyoxometalates as antibacterial agents for poultry based pathogens such as Salmonella typhimurium and Listeria monocytogenes.