Dye-Sensitized Heterogeneous Photocatalysts for Green Redox Reactions

Conversion of sunlight into chemical energy has been the subject of intense research efforts in recent years, due to the possibility to store the enormous amount of energy continuously provided by the Sun in the form of useful solar fuels. To allow such process, suitable photocatalysts are required, which are usually obtained by combination of different inorganic materials or by self-assembly of molecular components on semiconductor surfaces: accordingly, they are capable to carry out several different processes such as light harvesting, substrate binding, electron transport, storage and transfer. Among the photocatalytic systems developed to date, heterogeneous dye-sensitized semiconductors decorated with various electrocatalysts received particular attention, thanks to their favorable properties of tunable absorption spectrum, high stability and adaptability to different reactions. In this paper, we will review some selected examples of application of such photocatalysts to two main reactions, namely H+ reduction to H-2 and CO2 conversion to C-1-building blocks (CO, formate), which are among the most important transformations in the field of so-called artificial photosynthesis.