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

Electrocatalytic ammonia (NH 3 ) synthesis from the reduction of nitrate (NO 3 - ) is one of the effective and mild methods to treat nitrogen-containing wastewater from stationary sources and to obtain NH 3 readily compared with the Haber-Bosch process. However, the low efficiency of electrocatalytic NO 3 - reduction to NH 3 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 NH 3 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 (*NO 2 , *NO, and *NH 3 ). Density functional theory calculations demonstrate that Au SAs efficiently reduce the adsorption energy of *NO 3 - , and the newly formed Au-Cu bonds boost the reduction process of *NO 2 to *NO. Meanwhile, Au/Cu SAAs produce significantly less N 2 and N 2 O byproducts due to the prohibition of N-N coupling on single atoms, which finally leads to excellent Faradaic efficiency and NH 3 selectivity.