Comparison of the photoredox properties of polyoxometallates and semiconducting particles

We demonstrate that two large categories of compounds, namely, polyoxometallates (produced by acid condensation of mainly tungstates and/or molybdates) and aggregates of various metal oxides (formed by stirring, sonication etc) have similar properties. Emphasis is given to the photocatalytic properties of the two systems. The various steps in the photocatalytic cycles are described and several examples, from both systems, have been used to demonstrate that their photocatalytic performance is similar in terms of the overall mechanism of photodecomposition of organic compounds, the intermediate species involved and the final photodegradation products (i.e., CO2, H2O and inorganic anions).