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.