Carboxyl groups as active sites for H2O2 decomposition in photodegradation over graphene oxide/polythiophene composites

Graphene oxide (GO) or reduced graphene oxide (RGO) is an excellent promoter to improve the photodegradation activity of a hybridized photocatalyst in advanced oxidation processes (AOPs). However, the identification of active sites remains a challenge due to the complexity of GO surface with different oxygen functionalities and defects coexisted. In this work, we synthesized different GO/polythiophene (GO/PTh) composites via in-situ polymerization of thiophene monomers on different GO supports with controlled content of oxygen functionalities such as carboxyl, hydroxyl and epoxide bonds. GO-COOH/PTh shows the highest performance in the degradation of methylene blue (MB) and phenol under visible light among all GO/PTh catalysts. We find the degradation rate is determined by the amount of hydroxyl free radicals ( OH) via the reaction of photoelectrons with H 2 O 2 . Different oxygen groups on GO surface results in different photoelectron conversion efficiency (η, the ratio of degradation rate to photocurrent). More importantly, we find that η correlates linearly with the amount of COOH in the catalysts, indicating COOH groups act as active sites for OH generation during photodegradation. This study provides a deep understanding of active sites for H 2 O 2 decomposition in photo-assisted Fenton-like systems over GO containing photocatalysts.