Dual-Nitrogen Coordination Shell Engineering in o-B2N2 Monolayer Supported Dual-Atom Catalysts for Oxygen Reduction Reaction

Single-atom and dual-atom catalysts (SACs/DACs) have emerged as promising candidates for the oxygen reduction reaction (ORR), but it is still challenging due to the absence of robust substrates for simultaneously addressing the structure stability and activity issues. Herein, by using density functional theory (DFT) computations, a novel two-dimensional orthorhombic diboron dinitride (o-B₂N₂) monolayer with a narrow bandgap (0.66 eV) was developed and evaluated as an electrocatalyst substrate for ORR. A synergistic strategy involving dual transition metal atoms coordinated within a dual-nitrogen shell (TM-N-N) was employed to optimize the ORR performance. Remarkably, all TM₂@o-B₂N₂ monolayers based on 3d transition metals exhibit excellent thermal and electrochemical stability. Additionally, a di-iron centered o-B₂N₂ (Fe₂@o-B₂N₂) was identified among a series of TM₂@o-B₂N₂ monolayers, exhibiting superior ORR performance. The electrocatalytic activity was probed via crystal orbital Hamilton population (COHP), differential charge density, and molecular orbital analyses, revealing the electronic origins of the enhanced performance. The enhanced ORR activity of Fe₂@o-B₂N₂ originates from strong Fe-3d/N-2p orbital hybridization in the Fe-N-N coordination shell. The dual-nitrogen layer and di-metal sites synergistically modulate the d-band center, optimizing the adsorption of key species (e.g., *O₂/*OH) by facilitating electron redistribution from antibonding to bonding states, surpassing traditional h-BN and N-doped graphene counterparts. This work not only establishes Fe₂@o-B₂N₂ as an excellent ORR electrocatalyst, but also unveils a novel BN-like substrate material with broad applicability in electrocatalytic systems.