Electrochemical oxygen reduction reaction(ORR)with 2-electron process is an alternative for decentralized H2O2 production,but it remains high challenging to develop highly active and selective catalysts for this process.In this work,we present a selective and efficient nonprecious electrocatalyst,prepared through an easily scalable mild oxidation of single-walled carbon nanotubes(SWNTs)with different oxidative acids including sulfur acid,nitride acid and mixed sulfuric/nitric acids,respectively.The high-degree oxidized SWNTs treated by mixed acids exhibit the highest activity and selectivity of electroreduction of oxygen to synthesize H2O2 at low overpotential in alkaline and neutral media.Spectroscopic characterizations suggested that the C-O is vital for catalyzing 2-electron ORR,providing an insightful understanding of defected carbon surface as the active catalytic sites for 2-electron ORR.