Sustainable ammonia synthesis from nitrate wastewater via graphdiyne Mo-Cu-C≡C interfaces

Electrochemical green ammonia (NH₃) production using renewable electricity is sustainable but suffers from selectivity-activity-stability trade-off under industrial conditions. Here we report an atomic interface engineering strategy enabling in-situ assembly and coupling of hexaethynylbenzenes on molybdenum-copper oxidesto form an sp-hybridized Mo/Cu-C≡C heterointerface. It features dual d-orbital hybridization (Mo 4d-C 2p and Cu 3d-C 2p) weakening N-O bond by 36.85% and lowering activation barrier by 0.43 eV, reversible electron-buffer facilitating proton-coupled electron transfer, and self-regulated charge compensation between metal atoms and -C≡C- atomic wires, collectively endowing high activity and near-complete hydrogen evolution reaction suppression. The resulting catalyst achieves high NH₃ yielding rate (Y_NH3, 2.45 mmol h^-1 cm^-2) and Faradaic efficiency (~100%) under ambient conditions. A prototype flow electrolyzer operating with this catalyst sustains industrial-current densities of 500 mA cm^-2 for 300 hours with <3% activity decay, yielding potable water from nitrate wastewater. The membrane electrode assembly (MEA) achieves 380 h stable operation at the same current density with Y_NH3 of 3.64 mmol h^-1 cm^-2.