Photo-oxidation or photolysis of water (in photosynthesis) occurs in association of

Photo-oxidation or photolysis of water (in photosynthesis) occurs in association with PS II.
Photosystem II is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria.
The energized electrons are replaced by oxidizing water to form hydrogen ions and molecular oxygen. The hydrogen ions (protons) generated by the oxidation of water help to create a proton gradient that is used by ATP synthase to generate ATP.