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By means of density functional theory(DFT)computations,we systematically explored the potential of the single-sided chemically functionalized graphene by various functional groups as the metalefree electrocatalyst for oxygen reduction reaction in alkaline media.Our computations revealed that the spin density due to the single-sided functionalization at 12.5%ratio enhances O2 adsorption,and the O2 adsorption energies well correlate with the magnetic moments of C8R graphenes.C8F and C8(OCH3)graphenes with moderate magnetic moments exhibit appropriate chemical reactivity towards O2 activation.The following ORR elemental steps prefer to proceed through a 4e associative pathway,rather than the dissociative and 2e associative pathway.Both C8F and C8(OCH3)graphenes are promising ORR catalysts,and C8(OCH3)graphene is more efficient due to its lower overpotential.The present work provides an effective way to tune the catalytic performance of graphene for ORR by introducing a suitable spin density using its covalent functionalization.