Carbon foam (CF) is kind of light weight three dimensional reticular material consisting of plenty pores and interconnected hole walls with super adsorption capability. It has unique hollow structure which the electron hole pairs could transport freely along cylindrical nanostructure which supposed to overcome the recombination rate of the photo-generated electron-hole pairs. It also has great properties such as high conductivity, adjustable thermal and electrical conductivity, corrosion resistance and good thermal conductivity. Carbon foam can be the supporter for the photocatalyst to immobilized titanium dioxide and zinc oxide on carbon foam. Titanium dioxide (TiO2) and zinc oxide (ZnO) is well known as a photocatalyst for the removal of environmental pollutants. There are many methods can use to immobilize the titanium dioxide(TiO2) and zinc oxide(ZnO) on carbon foam for the photoreduction of heavy metals such as heat attachment method, hydrothermal method, spin coating and sol gel method. By using one of these technique, both photocatalyst can be immobilize on carbon foam.
Photocatalyst is defined as material or substances that is capable of absorbing light, producing electron–hole pairs that enable chemical transformations of the reaction participants and regenerate its chemical composition after each cycle of such interactions. Photocatalyst is a combination of “photo” which means the energy in the form of light and “catalyst” represents a compound that can activate reaction or fasten the reaction. There are two types of photocatalysic reactions which are homogeneous catalysis and heterogeneous catalysis. The reactant and photocatalyst in homogeneous catalysis exist in the same phase but they exist in different phases for heterogeneous catalysis.TiO2, ZnO, SnO2 and CeO2 are several types of semiconductors that been extensively used as heterogeneous photocatalysis since several decades. This is because of their biocompatibility, exceptional stability in a variety of conditions and capability to generate charge carriers when stimulated with required amount of light energy.
TiO2 is by far the most extensively investigated photocatalyst due to its photochemical stability, it can exhibit high photocatalytic activity, low cost, environmental friendly and non-toxic. Recently, other than TiO2, researcher have studied more about ZnO. The biggest advantages of ZnO in comparison to TiO2 is it can absorb over a large fraction of UV spectrum.