Ambient electrocatalytic N2 reduction to NH3 by metal fluorides

The high-temperature and high-pressure Haber-Bosch process for industrial NH3 production is rather energy-intensive with heavy CO2 emission. Electrochemical N-2 reduction in aqueous media offers an eco-friendly and sustainable alternative to ambient NH3 synthesis with the aid of efficient electrocatalysts for the N-2 reduction reaction (NRR), but they suffer from limited current efficiency for NH3 formation due to the unavoidable competing hydrogen evolution reaction (HER). Here, we report that LaF3 nanoplates act as a superb NRR electrocatalyst for ambient N-2-to-NH3 fixation with excellent selectivity due to their effective inhibition of the HER and activation of the NN triple bond. In 0.5 M LiClO4, they achieve a high faradaic efficiency of 16.0% and a large NH3 yield of 55.9 mu g h(-1) mg(cat.)(-1) at -0.45 V vs. the reversible hydrogen electrode, much higher than those of La2O3 (1.4%; 12.5 mu g h(-1) mg(cat.)(-1)) and most reported aqueous-based NRR catalysts. This catalyst also shows high long-term electrochemical and structural stability. The detailed NRR mechanism is also discussed.