Sequential electrocatalysis by single molybdenum atoms/clusters doped on carbon nanotubes for removing organic contaminants from wastewater

Oxygen reduction reaction (ORR) can realize the goal of in-situ H2O2 generation. A suitable catalyst ensures a proper binding strength between the electrocatalyst and the intermediate (i.e., *OOH), thereby avoiding the 4-electron ORR process and H2O production. Herein, we demonstrate that single molybdenum (Mo) atoms/clusters doped on carbon nanotubes can effectively alter the ORR pathway to generate H2O2; meanwhile, the established sequential ORR system for H2O2 production can tandemly remove ibuprofen (IBU) and other organic contaminants from water and wastewater. The results reveal that single atomic Mo clusters preferentially acted as the active sites that are merely required to overcome 0.11 eV downhill to form *OOH. Surprisingly, this tandemly constructed ORR with in-situ generated H2O2 performed better than the in-vitro H2O2 system. These findings offer a promising solution to reduce the costs related to the production and transportation of H2O2 for various applications, including the oxidation and removal of emerging organic contaminants from water and wastewater.