Electrocatalytic Reduction of Nitrate to Ammonia via a Au/Cu Single Atom Alloy Catalyst

Electrocatalytic ammonia (NH₃) synthesis from the reduction of nitrate (NO₃^-) is one of the effective and mild methods to treat nitrogen-containing wastewater from stationary sources and to obtain NH₃ readily compared with the Haber-Bosch process. However, the low efficiency of electrocatalytic NO₃^- reduction to NH₃ on traditional Cu-based catalysts hinders their practical application. Here, we prepare a Au/Cu single atom (SA) alloy (Au/Cu SAA) that shows a high performance of NH₃ synthesis with 99.69% Faradaic efficiency at -0.80 V vs RHE. The structures of Au SAs and alloyed Au/Cu are confirmed by the detailed characterizations. Online differential electrochemical mass spectrometry confirms the occurrence of key reaction intermediates (*NO₂, *NO, and *NH₃). Density functional theory calculations demonstrate that Au SAs efficiently reduce the adsorption energy of *NO₃^-, and the newly formed Au-Cu bonds boost the reduction process of *NO₂ to *NO. Meanwhile, Au/Cu SAAs produce significantly less N₂ and N₂O byproducts due to the prohibition of N-N coupling on single atoms, which finally leads to excellent Faradaic efficiency and NH₃ selectivity.