Ambient electrocatalytic N2 reduction to NH3 by metal fluorides

Abstract

The high-temperature and high-pressure Haber–Bosch process for industrial NH₃ production is rather energy-intensive with heavy CO₂ emission. Electrochemical N₂ reduction in aqueous media offers an eco-friendly and sustainable alternative to ambient NH₃ synthesis with the aid of efficient electrocatalysts for the N₂ 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 N₂-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 μg h⁻¹ mg_cat.⁻¹ at −0.45 V vs. the reversible hydrogen electrode, much higher than those of La₂O₃ (1.4%; 12.5 μg 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.