Degradation of microcystin-LR with expanded graphite based photocatalysts: Performance and mechanism based on active sites-radicals interaction

Expanded graphite based Z-scheme photocatalysts (EGP) were developed to achieve the efficient degradation of microcystin-LR (MC-LR) in water. Results show that EGP-TC-5 can achieve a complete removal of MC-LR with 5 h visible light irradiation. In the degradation process, the clean-up of Adda side chain, the ring opening and decarboxylate have been proven to be the crucial steps in the degradation process, and h⁺ and ·O₂^– are considered as the main radical species in the photocatalytic process. More importantly, we first revealed that h⁺ prefers to induce the reaction for the clean-up of the Adda side chain, while ·O₂^– shows the preference to conduct the ring-open reaction. Specific active sites for the major degradation reactions have been put forward with frontier electron densities (FEDs) and point charges calculations. The theoretical calculation results are highly consistent with the experimental results, providing new insight into the degradation process of MC-LR.