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The oxygen reduction reaction (ORR) is the key bottleneck in the performance of fuel cells. The rational design of efficient and inexpensive ORR electrocatalysts is a common goal for the large-scale application of fuel cells. Herein, by means of density functional theory calculations, we demonstrate that two-dimensional (2D) biphenylene (BPN) with doping B/N are metal-free single-atom catalyst candidates with the overpotentials comparable to those noble metal benchmark catalysts. The B/N doping effectively modulates the charge distribution in BPN sheets, promotes the electron transfer between doped BPN and the oxygen-containing intermediates, which results in enhancing their binding strength, and facilitating their electrochemical ORR catalytic activity. This work not only provides metal-free single-atom catalysts for ORR, but also promotes BPN nanomaterials for single-atom catalysts development and practical applications. [Display omitted] • 2D biphenylene with doping B/N are metal-free single-atom catalysts. • N 2 -BPN exhibits superior ORR performance with a overpotential of 0.40 V. • N substituting C 2 atom in BPN could tune charge redistribution of active C 1 atom. • N 2 -BPN exhibits a suitable adsorption free energy and shows high ORR activity. [ABSTRACT FROM AUTHOR]