Photocatalytic Water Splitting

Photocatalytic water splitting uses light striking a catalyst to break water down into hydrogen and oxygen, but unlike a photoelectrochemical cell, which relies on solid electrodes, it works through an irradiated dispersion of catalyst particles suspended directly in the water. When a photon carrying more than 1.23 electron volts of energy strikes the semiconductor catalyst, it creates an electron and a hole that react with water molecules at the catalyst surface, together splitting two water molecules into two hydrogen molecules and one oxygen molecule. The approach is considered an important strategy for producing renewable hydrogen fuel as an alternative to petroleum, but it remains more hypothetical than practical, since no water splitting system driven by solar radiation has yet been commercialized, held back by low efficiency and by the catalyst materials themselves breaking down over time.