Plastic Degradation by Photocatalysis: Basic Concepts and General Mechanisms

Owing to their several desirable properties, plastics have brought a lot of convenience to us and have become an integral part of our lives. However, being non-biodegradable, the disposal and treatment of waste plastic remain a ubiquitous issue. Conventional treatment strategies may not be able to satisfactorily break the C-C, C-O or C-H bonds inherently present in their structures. Photocatalysis presents one of the promising routes for addressing the growing need of plastic waste treatment/disposal. This approach employs semiconductor materials as photocatalysts. When exposed to light of appropriate wavelength, these photocatalysts generate electron-hole pairs that initiate redox reactions, forming highly reactive oxygen species (ROS) such as hydroxyl radicals. These ROS can effectively break down polymer chains in plastics through a series of oxidative reactions, ultimately leading to polymer fragmentation or even complete mineralization to CO2 and water. This chapter discusses the basic principles of photocatalysis, the photocatalytic method and the general mechanism involved in the degradation of plastics.