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As proton-exchange membrane fuel cell technology has grown and developed, there has been increasing demand for the design of novel catalyst architectures to achieve high power density and realize wide commercialization. Herein, based on the two-dimensional biphenylene, we compare the oxygen reduction reaction (ORR) activity on the active sites with different biaxial lattice strains using first-principles calculations. The ORR free energy diagrams of biphenylene monolayers with varying lattice strains suggest that the biaxial tensile strains are unfavorable for catalytic activity. In contrast, the biaxial compressive strains could improve the catalytic performance. The biphenylene systems with the strain of −2% ∼ −6% (S -0.02∼-0.06) display overpotentials of 0.37–0.49 V. This performance is comparable to or better than the Pt (111) surface. The Bader charge transfer of adsorbed O species on various biaxial strain biphenylene catalysts could be a describer to examine the catalytic activity. The catalysts possessed the moderate transferred charge of O adsorbed species often promotes catalytic process and give the high catalysis efficiency. Overall, this work suggests that the lattice strain strategy can significantly enhance the catalytic activity of biphenylene materials and further provide guidance to design biphenylene-based catalysts in various chemical reactions. [Display omitted] • Lattice strains in 2D biphenylene could enhance ORR activity. • Compressive strains of −2% ∼ −6% endow their overpotentials of 0.37–0.49 V. • Charge transfer of adsorbed O species is a descriptor to examine ORR performance. • Moderate strains and moderate transferred charge lead to excellent efficiency. [ABSTRACT FROM AUTHOR]

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]