Probing the formation mechanisms of reactive oxygen species in graphene oxide-catalyzed ozone advanced oxidation processes

Abstract

Graphene oxide (GO), a representative carbon-based catalyst, has demonstrated promising prospects for oxidation removal of organic pollutants in ozone (O₃)-based advanced oxidation processes (AOPs). However, due to complex reactions of realistic ozonation processes, the functional mechanisms of oxygen-containing functional groups of GOs remain ambiguous, which are generally difficult to identify by single experimental characterization. Herein, we applied density functional theory (DFT) to investigate the physical interactions and chemical reaction mechanisms between O₃ and oxygen-containing functional groups of GO in aqueous media. It is demonstrated that the functional groups on GOs could promote the generation of various reactive oxygen species (ROS) through different ozonation mechanisms, which include direct activation and indirect H-abstraction. The connection between types of functional groups and the generated ROS has been established. Further reactive molecular dynamics simulations were used to dynamically capture the catalytic ozonation events for the functional groups of GOs. The simulated type changes of functional groups and time evolution of the ROS-related species number show consistent behavior with the above DFT computations. The proposed mechanisms provide an improved understanding of ozonation catalysis, which is expected to advance the development of AOP technologies utilizing GO catalysis.