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 H 2 O 2 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 H 2 O production. Herein, we demonstrate that single molybdenum (Mo) atoms/clusters doped on carbon nanotubes can effectively alter the ORR pathway to generate H 2 O 2 ; meanwhile, the established sequential ORR system for H 2 O 2 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 H 2 O 2 performed better than the in-vitro H 2 O 2 system. These findings offer a promising solution to reduce the costs related to the production and transportation of H 2 O 2 for various applications, including the oxidation and removal of emerging organic contaminants from water and wastewater.