Sustainable synthesis of NH­3 via electrochemical reduction of N2 on an earth abundant Cu gas diffusion electrode at ambient conditions

The electrochemical reduction of N₂ to produce NH₃ at ambient conditions is an effective and sustainable route to store H₂, balance the N₂ cycle, and provide means to produce on-demand fertilizers. The efficient electrosynthesis of NH₃ is challenging because of the high energy of N ≡ N triple bond (941 kJ/mol), dominant undesired H₂ evolution reaction (HER), and lower solubility of N₂ in aqueous solution. Here, we propose theory-guided activity descriptors to identify an efficient N₂ reduction reaction (NRR) catalyst, followed by its implementation in a flow through gas diffusion electrode (GDE) to quantify the effects of pH, cation identity, H₂O saturation, and N₂ concentration on the kinetics of the NRR. The identified Cu catalyst with dominant (111) facets electrodeposited on a carbon paper provides optimal active sites to obtain maximum NH₃ Faradaic efficiency (FE) of 18 ± 3 % at -0.3 V vs RHE and the maximum NH₃ current density of 0.25 ± 0.03 mA/cm² at -0.5 V vs RHE in an alkaline medium. The electrolyte pH, counter cations and the H₂O saturation on the catalyst are optimized to suppress the HER. The fixed potential DFT calculations reveal an associative distal mechanism for the NRR over Cu where the hydrogenation of *N₂ is the rate limiting step.