Introduction and Objective
Hydrogen is an important basic chemical. It is widely used in industry for example methanol synthesis, the Haber-Bosch process, hydrogenation reactions or the Fischer-Tropsch process. Furthermore, over the last decades it has become evident that CO2 is a greenhouse gas, which is presumably responsible for global warming. Thus and due to its limited availability, humankind will have to change from fossil fuels as primary energy sources to regenerative energy sources. H2 is promising candidate as an energy carrier. Lately, research is focusing on pollution free hydrogen generation by photocatalytic water splitting or photoelectrolysis of water. These methods provide sustainable energy.