When light irradiates the photocatalyst, it excites electrons from the valence band to the conduction band, creating electron-hole pairs. These pairs migrate to the surface of the catalyst and participate in redox reactions with water and oxygen. The overall mechanism involves:
1. Light Absorption: The photocatalyst absorbs photons and generates electron-hole pairs. 2. Charge Separation: Electrons and holes separate and migrate to the catalyst surface. 3. Redox Reactions: Electrons reduce oxygen to form superoxide radicals, while holes oxidize water to produce hydroxyl radicals. 4. Pollutant Degradation: These reactive species attack and degrade organic and inorganic pollutants in water.
