Predicting the Mechanisms for H₂O₂ Activation and Phenol Oxidation Catalyzed by Modified Graphene-Based Systems Using Density Functional Theory

The heterogeneous Fenton-like reaction on metal-free graphene-based catalysts attracts great attention. However, a systematic and comprehensive understanding of the mechanisms for H₂O₂ activation and pollutant oxidation is still lacking. In this study, the heterogeneous Fenton-like mechanisms on doped and oxygen-containing graphene are investigated using density functional theory. The H₂O₂ tends to form a surface oxygen and a water molecule on the doped graphene. For the oxygen-containing graphene-based systems, relative to the groups in the basal plane, the separated groups on the edge including hydroxyl, carbonyl, and carboxyl readily activate H₂O₂ to hydroxyls. However, when the groups are close to each other, more additional side reactions might occur upon H₂O₂ adsorption, which may inhibit catalyst retrieval. Phenol is selected as a model pollutant to study its oxidation reaction with the adsorbed oxygen formed from the dissociated H₂O₂. The thermodynamics of the reactions depends significantly on the co-adsorption strengths over different catalysts. Our work provides key fundamental insights into the catalytic performance of various modified graphene-based systems, which could guide the future design and applications of heterogeneous Fenton reactions.