Chapter 1 - Introduction

Abstract

Currently, catalysis is defined as the acceleration of a chemical reaction assisted by a species known as a catalyst. Catalysis was among the very first applications of nanoparticles, which are indisputably the most important industrial catalysts with a wide array of applications from energy conversion and storage to chemical manufacturing. Catalysis is dividable into three major classes: biological, homogeneous, and heterogeneous catalysis. The fascinating properties of heteropoly acids, such as tunable acidity and redox properties, high thermal stability, inherent resistance to oxidative decomposition, and striking sensitivity to light and electricity, have made them excellent candidates for catalytic purposes. Under moderate conditions, many photocatalytic reactions take place readily in the presence of heteropoly acids. More significantly, the photooxidation properties are very suitable for the degradation of a variety of aqueous organic pollutants and their photoreduction properties can be utilized to remove transition metal ions from water. A number of Keggin- and Dawson-type heteropoly acids have been utilized as oxidative and reductive electrocatalysts. Each heteropoly acid demonstrates featured electrochemical behavior because of its particular redox potential, pKa, and stability. In the last decade, the syntheses and applications of nanocompounds have been under the spotlight. In this regard, polyoxometalates are attracting a good deal of attention as building blocks for functional composite materials owing to their fascinating nano-sized structures.