Materials for Photoelectrochemistry and Water Splitting
One of the promising technologies for future alternative energy sources is the direct conversion of sunlight into chemical and electrical energy by using photocatalysis or photoelectrochemical cells (PEC), respectively. The greatest challenge in these fields is to develop new types of advanced materials with the desired electrical and optical properties that will replace the conventional raw materials that are currently used. Photocatalysis has attracted great interest over the last decades, especially for its potential to produce clean and cheap renewable energy without dependence on fossil fuels and without carbon dioxide emission.
Photocatalysis applications span from many fields such as: solar fuel production, water splitting, photo-degradation of pollutants, and catalysis of other chemical reactions, e.g. for the production of fine chemicals. The second system is based on photo electrochemical cell (PEC) which is based on semiconductor-liquid junctions which can be relatively efficient with respect to the first system, due to improvement of charge separation under illumination. The PECs can be used in order to convert the solar radiation into chemical energy (i.e. water splitting) or to electric energy (i.e. solar cells). Typically for efficient photo (electro) catalysis, an additional co-catalyst, which is currently mostly based on noble metals, is needed in order to increase the wanted reaction activity and rate.
Although in the last years a significant progress has been made in this field, it is still an essential task to find efficient and low cost materials as photoactive materials and co-catalysts. More importantly, it is necessary to gain a basic understanding of the physical properties and the fundamental operation mechanisms in this field.