Electrochemical ammonia synthesis by reduction of nitrate on Au doped Cu nanowires

Electrochemical nitrate reduction reaction (NO₃ ^-RR) to synthesize valuable ammonia (NH₃) is considered as a green and appealing alternative to enable an artificial nitrogen cycle. However, as there are other NO₃ ^-RR pathways present, selectively guiding the reaction pathway towards NH₃ is currently challenged by the lack of efficient catalyst. Here, we demonstrate a novel electrocatalyst for NO₃ ^-RR consisting of Au doped Cu nanowires on a copper foam (CF) electrode (Au-Cu NWs/CF), which delivers a remarkable NH₃ yield rate of 5336.0 ± 159.2 μg h^-1 cm^-2 and an exceptional faradaic efficiency (FE) of 84.1 ± 1.0% at -1.05 V (vs. RHE). The ¹⁵N isotopic labelling experiments confirm that the yielded NH₃ is indeed from the Au-Cu NWs/CF catalyzed NO₃ ^-RR process. The XPS analysis and in situ infrared spectroscopy (IR) spectroscopy characterization results indicated that the electron transfer between the Cu and Au interface and oxygen vacancy synergistically decreased the reduction reaction barrier and inhibited the generation of hydrogen in the competitive reaction, resulting in a high conversion, selectivity and FE for NO₃ ^-RR. This work not only develops a powerful strategy for the rational design of robust and efficient catalysts by defect engineering, but also provides new insights for selective nitrate electroreduction to NH₃.