Graphene-Based Materials for Photocatalytic Degradation of Organic Pollutants

Graphene, a two-dimensional layered material, is considered the wonder discovery of recent times, with applications in optoelectronics, sensors, photocatalytic dye degradation, energy applications, and many more. A few-layer graphene is semimetallic with a zero band gap, high electronic conductivity, high transparency, and a high theoretical surface area. Photocatalytic degradation of organic pollutants is an essential area of research where graphene plays an important role as a substrate material. Without an inherent band gap, pristine graphene is not so much useful in photocatalysis. However, graphene oxide or reduced graphene oxide with surface oxygenated functional groups and with an effective band gap is useful for harvesting solar light and using it for UV–visible to near-infrared (NIR) photocatalysis. Graphene oxide shows excellent results when used in composite with other semiconductor metal oxides, metal sulfides, or carbon-based semiconductors (viz. graphitic carbon nitride) in organic pollutants degradation under solar light illumination. This is because the π–π network in graphene provides excellent support for organic pollutants. Besides, the oxygenated surface groups trap photogenerated electrons and prohibit electron–hole recombination and the extended π-network acts as an accumulator and transporter of photogenerated electrons. In this chapter, we focus on the photocatalytic degradation of harmful organic pollutants present in water with graphene-based composites, such as graphene-metal nanoparticles; graphene-semiconductor metal oxides, and graphene-graphitic carbon nitride.