ABSTRACT
In this entry, solar light–based hydrogen production methods from water are introduced and explained. Solar energy is the most abundant form of energy on Earth and water is the most abundant source of hydrogen. Thus, generating hydrogen from water with solar energy is a sustainable and promising technology for clean energy production. In the first part of the entry, background information is presented regarding specific photophysical and photochemical processes relevant to water dissociation with light energy to generate hydrogen. The physics of photoexcited states is discussed, as well as photocatalytic reaction mechanisms (both heterogeneous and homogeneous). A classification of light–based hydrogen production systems from water is given and three systems are analyzed: photoelectrochemical cell, dye‐sensitized tandem photoelectrochemical cell, and photochemical reactors with supramolecular devices for homogeneous photocatalysis. At the end of the entry, an illustration shows a combined system that couples a photooxidation reactor and a photoreduction reactor to conduct a complete water splitting process. A relatively low efficiency is compensated by an inexpensive cost.
