Polarized Cu–Bi Site Pairs for Non-Covalent to Covalent Interaction Tuning toward N₂ Photoreduction

A universal atomic layer confined doping strategy is developed to prepare Bi₂₄O₃₁Br₁₀ materials incorporating isolated Cu atoms. The local polarization can be created along the Cu-O-Bi atomic interface, which enables better electron delocalization for effective N₂ activation. The optimized Cu-Bi₂₄O₃₁Br₁₀ atomic layers show 5.3× and 88.2× improved photocatalytic nitrogen fixation activity than Bi₂₄O₃₁Br₁₀ atomic layer and bulk Bi₂₄O₃₁Br₁₀, respectively, with the NH₃ generation rate reaching 291.1 µmol g⁻¹ h⁻¹ in pure water. The polarized Cu–Bi site pairs can increase the non-covalent interaction between the catalyst's surface and N₂ molecules, then further weaken the covalent bond order in N-N. As a result, the hydrogenation pathways can be altered from the associative distal pathway for Bi₂₄O₃₁Br₁₀ to the alternating pathway for Cu-Bi₂₄O₃₁Br₁₀. This strategy provides an accessible pathway for designing polarized metal site pairs or tuning the non-covalent interaction and covalent bond order.