Artificial photosynthesis is a way to mimic photosynthesis in nature. From Wikipedia:
A research field that attempts to replicate the natural process of photosynthesis, which is a process that converts sunlight, water, and carbon dioxide into carbohydrates and oxygen. Splitting water into hydrogen and oxygen by using sunlight energy is referred to as photo-electrolysis.
A sample of a photoelectric cell in a lab environment. Catalysts are added to the cell, which is submerged in water and illuminated by simulated sunlight. The bubbles seen are oxygen (forming on the front of the cell) and hydrogen (forming on the back of the cell).
The actual process that allows half of the overall photosynthetic reaction to take place is photo-oxidation. This half-reaction is essential in separating water molecules because it releases hydrogen and oxygen ions. These ions are needed to reduce carbon dioxide into a fuel. However, the only known way this is possible is through an external catalyst, one that can react quickly as well as constantly absorb the sun’s photons. The general basis behind this theory is the creation of an “artificial plant” type fuel source.
A triad assembly, with a photosensitizer (P) linked in tandem to a water oxidation catalyst (D) and a hydrogen evolving catalyst (A). Electrons flow from D to A when catalysis occurs.