Photodegradation involves several steps: 1. Photon Absorption: The catalyst absorbs light, usually in the UV or visible spectrum. 2. Electron-Hole Pair Generation: The absorbed energy excites electrons from the valence band to the conduction band, creating electron-hole pairs. 3. Formation of Reactive Species: These pairs generate reactive oxygen species (ROS) like hydroxyl radicals (•OH) and superoxide radicals (O2•-). 4. Pollutant Degradation: The ROS attack and break down the pollutants into smaller, often less harmful molecules.
