Insight into the mechanism of excellent visible-light photocatalytic activity of TiO2/graphene nanocomposite for photodegradation of organic pollutants in water

We developed a graphene oxide-free synthetic route to hybridize TiO2/graphene at nanoscale with an excellent visible-light photocatalytic activity for the degradation of methylene blue; however, the mechanism behind this superior activity was a mystery. In this study, we performed radical scavenger tests, electron paramagnetic resonance measurements, and photoluminescence measurements in order to uncover the origin of the excellent activity of the TiO2/graphene nanocomposite. The TiO2/graphene nanocomposite exhibited an excellent ability in absorbing organic pollutants, a high efficiency of charge carrier separation, and a great ability to activate adsorbed oxygen molecules and subsequently trap superoxide radicals. We have found that the high ability to activate adsorbed oxygen molecules and trap superoxide radicals of the TiO2/graphene nanocomposite was the key factor contributing to its superior visible-light photocatalytic activity.